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dlc-eeciv.jpg Diagnostic Link Connectors for EEC-IV processors ('84-95).
'84-86 (red) located on R wheelwell near starter relay.
'87-95 (black or gray) located under L hood hinge under EEC TEST cover. (WPT-743 & WPT-352)
'94-96 Bronco - do not confuse with RED 4WABS connector also under L hood hinge

'96-up use OBD-II, and this DLC:
[url=http://www.supermotors.net/vehicles/registry/media/174488][img]http://www.supermotors.net/getfile/174488/thumbnail/dlc96broncoc201.jpg[/img][/url] . [url=http://www.supermotors.net/registry/media/738423][img]http://www.supermotors.net/getfile/738423/thumbnail/autelal309.jpg[/img][/url]

Connect FP Relay (terminal A) to any ground (like terminal E) to force the fuel pump(s) on when the key is in RUN.

[url=http://www.supermotors.net/registry/media/862996][img]http://www.supermotors.net/getfile/862996/thumbnail/dlcjumper.jpg[/img][/url] . [url=http://www.supermotors.net/registry/media/892730][img]http://www.supermotors.net/getfile/892730/thumbnail/eecconnectors.jpg[/img][/url]

Pins D & F are a primitive SCP bus, but on these old vehicles, nothing else was networked in.

Connect pin 1 (209 W/Pu) to any ground (like terminal E) with any jumper wire (like a paperclip) to trigger diagnostic modes.  (See the NEXT diagram.)  Consult [url=http://www.fordf150.net/forums/viewtopic.php?t=71346]the 7th post on this page[/url] for the compete procedure to pull codes & trigger all test modes.  If the CEL is burned out, connect CEL (C) to a 12V test light, and the light's other terminal to a 12V source on the same vehicle.

To hardwire a self-test switch in the dash, see:
[url=http://www.supermotors.net/registry/media/904955][img]http://www.supermotors.net/getfile/904955/thumbnail/selftestswitch.jpg[/img][/url]

[url=http://www.fourdoorbronco.com/board/showthread.php?t=5226]Automotive Terms & Abbreviations[/url]
[url=http://www.troublecodes.net/Ford/]EEC-IV DTC definition list[/url]
[url=http://www.oldfuelinjection.com/?p=13]Ryan's page similar to this one[/url]

No matter what code you get, DON'T PICK THE NAME OF A PART OUT of the code definition - read the WHOLE definition, and then confirm the condition it indicates.  If the condition doesn't exist, clear the code and see how long it takes to re-set that code.  If the condition DOES exist, learn about the system to identify EVERY possible cause of the condition.  For instance: if the EVP doesn't indicate the EGR is opening, that doesn't mean to replace either of them.  It could simply be a vacuum leak in one of the lines, or the reservoir.

If spurious or false codes are delivered, remove the EEC & inspect its PC board for leaking capacitors.

[url=http://www.supermotors.net/registry/media/901696][img]http://www.supermotors.net/getfile/901696/thumbnail/eecburned9258e4oda2z.jpg[/img][/url]

For voltage faults &/or contradictory faults, repair the battery terminals first:

[url=https://www.supermotors.net/registry/2742/69178-4][img]https://www.supermotors.net/getfile/723279/thumbnail/07done.jpg[/img][/url]

Conditions: o = Key On Engine Off (KOEO), r = Engine Running (KOER), c = Continuous Memory
NO CODES Unable to initiate Self-Test or unable to output Self-Test codes (replace MIL bulb, inspect PC board inside EEC, read TSB below)
---------2-digit codes used until 1991---------
11 orc System PASS
12 r Cannot control rpm during Self-Test high rpm check
13 r Cannot control rpm during Self-Test low rpm check
14 c PIP circuit failure (gas); tach sensor failure (diesel)
15 o EEC processor Read Only Memory (ROM) test failed
15 c EEC processor Keep Alive Memory (KAM) test failed
18 r SPOUT circuit open
18 c Loss of IDM input to processor/SPOUT circuit grounded
19 o Failure in EEC processor internal voltage
21 or Engine Cooling Temperature (ECT) sensor out of Self-Test range (engine not warmed up before test)
22 orc Manifold Absolute Pressure (MAP) sensor out of Self-Test range
23 orc Throttle Position (TP) sensor out of Self-Test range
24 or Air Charge Temperature (ACT) sensor out of Self-Test range
25 r Knock not sensed during Dynamic Response Test (operator error)
26 or Transmission Fluid Temp (TFT) out of Self-Test range (engine not warmed up before test)
29 c Insufficient Vehicle Speed Signal (VSS) input
31 orc EVP circuit below minimum voltage
32 orc EVP voltage below closed limit
33 rc EGR valve opening not detected (no change in EVP when EVR activated)
34 orc EVP voltage above closed limit
35 orc EVP circuit above maximum voltage
41 r HEGO sensor circuit indicates system lean
41 c No HEGO switching detected
42 r HEGO sensor circuit indicates system rich
43 c Throttle Position (TP) sensor below idle spec
44 r Thermactor air system inoperative (TAB or TAD open circuit)
45 r Thermactor air upstream/misdirected during KOER
46 r Thermactor air not bypassed during KOER
47 o 4x4 switch closed during test (operator error)
49 c 1-2 Shift error
51 oc ECT indicated -40°C (-40°F)/circuit open
52 o Power Steering Pressure Switch (PSPS) circuit open
52 r PSPS circuit did not change states during Dynamic Response Test (operator error)
53 oc TP above maximum voltage
54 oc ACT indicated -40°C (-40°F)/circuit open
56 oc Transmission Fluid Temp (TFT) indicated -40°C (-40°F)/circuit open
59 c 2-3 Shift error
61 oc ECT indicated 123°C (254°F)/circuit grounded
62 c Torque Converter Clutch error
63 oc TP circuit below minimum voltage
64 oc ACT indicated 123°C (254°F)/circuit grounded
65 r Transmission Control Switch (TCS) circuit did not change states during Dynamic Response Test (operator error)
66 oc Transmission Fluid Temp (TFT) indicated 143°C (290°F)/circuit grounded
67 o Neutral Drive Switch (NDS) circuit open; A/C or Defrost on (Manual) during test (operator error)
68 c Transmission Fluid Temp (TFT) transmission over temp (over-heated)
69 c 3-4 Shift error
72 r Insufficient MAP change during Dynamic Response Test (operator error)
73 r Insufficient TP change during Dynamic Response Test (operator error)
74 rc Brake On/Off (BOO) circuit open or not actuated during Self-Test (operator error)
77 r Operator error during Dynamic Response Test
81 o Air Management 2 (AM2/TAD) circuit failure
82 o Air Management 1 (AM1/TAB) circuit failure
84 o EGR Vacuum Regulator (EVR) circuit failure
85 o Canister Purge (CANP) circuit failure
87 oc Primary fuel pump circuit failure
91 o Shift Solenoid 1 (SS1) circuit failure
92 o Shift Solenoid 2 (SS2) circuit failure
93 o Coast Clutch Solenoid (CCS) circuit failure
94 o Torque Converter Clutch (TCC) solenoid circuit failure
95 oc Fuel Pump circuit open - EEC processor to motor ground (fuel pump unplugged or wiring damage)
96 oc Fuel Pump circuit open - battery to EEC processor (inertia switch tripped or FP relay failed)
97 o Transmission Control Indicator Lamp (TCIL) circuit failure
98 r Hard fault present
99 oc Electronic Pressure Control (EPC) circuit failure
2-digit codes------------1991------------3-digit codes
111 orc System PASS
112 oc ACT indicated 123°C (254°F)/circuit grounded
113 oc ACT indicated -40°C (-40°F)/circuit open
114 or Air Charge Temperature (ACT) Sensor out of Self-Test range
116 or Engine Cooling Temperature (ECT) Sensor out of Self-Test range (engine not warmed up before test)
117 oc ECT indicated 123°C (254°F)/circuit grounded
118 oc ECT indicated -40°C (-40°F)/circuit open
121 orc Throttle Position (TP) Sensor out of Self-Test range
121 rc Throttle position voltage inconsistent with MAF sensor (vacuum leak downstream of MAF)
122 oc TP circuit below minimum voltage
123 oc TP above maximum voltage
124 rc Throttle Position (TP) sensor voltage higher than expected
125 rc Throttle Position (TP) sensor voltage lower than expected
126 orc Manifold Absolute Pressure (MAP) Sensor out of Self-Test range
128 c MAP vacuum circuit failure
129 r Insufficient MAP change during Dynamic Response Test (operator error)
136 c System indicates lean (Bank #2)
137 r System indicates lean (Bank #2)
157 orc Mass Air Flow (MAF) sensor circuit below minimum voltage
158 orc Mass Air Flow (MAF) sensor circuit above maximum voltage
159 orc Mass Air Flow (MAF) sensor circuit voltage higher or lower than expected
167 r Insufficient TP change during Dynamic Response Test (operator error)
171 c Fuel system at adaptive limits, Oxygen Sensor (HEGO) unable to switch, Bank 1
172 rc Lack of Oxygen Sensor (HEGO) switches, indicates lean, Bank 1
173 rc Lack of Oxygen Sensor (HEGO) switches, indicates rich, Bank 1
175 c Fuel system at adaptive limits, Oxygen Sensor (HEGO) unable to switch, Bank 2
176 rc Lack of Oxygen Sensor (HEGO) switches, indicates lean, Bank 2
177 rc Lack of Oxygen Sensor (HEGO) switches, indicates rich, Bank 2
179 c Fuel system at lean adaptive limit at part throttle, system rich, Bank 1
181 c Fuel system at rich adaptive limit at part throttle, system lean, Bank 1
184 orc Mass Air Flow (MAF) sensor voltage higher than expected
185 orc Mass Air Flow (MAF) sensor voltage lower than expected
186 orc Injector pulsewidth higher than expected (with BARO/MAP sensor)
186 orc Injector pulsewidth higher or mass air flow lower than expected (without BARO/MAP sensor)
187 orc Injector pulsewidth lower than expected (with BARO/MAP sensor)
187 orc Injector pulsewidth lower or mass air flow higher than expected (without BARO/MAP sensor)
188 c Fuel system at lean adaptive limit at part throttle, system rich (Bank #2)
189 c Fuel system at rich adaptive limit at part throttle, system lean (Bank #2)
211 c PIP circuit failure
212 c Loss of IDM input to processor/SPOUT circuit grounded
213 r SPOUT circuit open
214 orc Cylinder Identification (CID/CPS) circuit failure
215 orc PCM detected coil 1 primary circuit failure (EI/EDIS)
216 orc PCM detected coil 2 primary circuit failure (EI/EDIS)
217 orc PCM detected coil 3 primary circuit failure (EI/EDIS)
218 orc Loss of Ignition Diagnostic Monitor (IDM) signal-left side (dual plug EI/EDIS)
222 orc Loss of Ignition Diagnostic Monitor (IDM) signal-right side (dual plug EI/EDIS)
223 orc Loss of Dual Plug Inhibit (DPI) control (dual plug EI/EDIS)
224 orc PCM detected coil 1, 2, 3 or 4 primary circuit failure (dual plug EI/EDIS)
225 r Knock not sensed during Dynamic Response Test (operator error)
226 orc Ignition Diagnostic Monitor (IDM) signal not received (EI/EDIS)
232 orc PCM detected coil 1, 2, 3 or 4 primary circuit failure (EI/EDIS)
311 r Thermactor air system inoperative (Bank #1 w/dual HO2S)
312 r Thermactor air upstream/misdirected
313 r Thermactor air not bypassed
327 orc EVP circuit below minimum voltage
328 orc EVP voltage below closed limit
332 rc EGR valve opening not detected
334 orc EVP voltage above closed limit
334 orc EVP closed voltage higher than expected
335 o EGR (PFE) sensor voltage higher or lower than expected
336 orc Exhaust pressure high; PFE/DPFE circuit voltage higher than expected
337 orc EGR (EVP/PFE) circuit above maximum voltage
341 orc Octane adjust service pin open
411 r Cannot control rpm during low rpm check
412 r Cannot control rpm during high rpm check
452 c Insufficient Vehicle Speed Signal (VSS) input
511 o EEC processor Read Only Memory (ROM) test failed
512 c EEC processor Keep Alive Memory (KAM) test failed
513 o Failure in EEC processor internal voltage
519 o Power Steering Pressure (PSP) switch circuit open
521 r Power Steering Pressure (PSP) switch circuit did not change states (operator error)
522 o Vehicle not in PARK or NEUTRAL during KOEO test (operator error)
528 c Clutch switch circuit failure
536 r Brake On/Off (BOO) circuit failure/not actuated during Dynamic Response Test (operator error)
538 r Insufficient RPM change during Dynamic Response Test (operator error)
538 r Invalid cylinder balance test due to throttle movement during test (operator error)
538 r Invalid cylinder balance test due to CID circuit failure
539 or A/C on/Defrost on during test (operator error)
542 oc Fuel Pump circuit open - EEC processor to pump motor (no ground with FP relay OFF)
543 oc Fuel Pump circuit open - battery to EEC processor (no power with FP relay ON)
551 o Idle Air Control (IAC) circuit failure
552 o Air Management 1 (AM1/TAB) circuit failure
553 o Air Management 2 (AM2/TAD) circuit failure
556 oc Primary fuel pump circuit failure
558 o EGR Vacuum Regulator (EVR) circuit failure
565 o Canister Purge (CANP) circuit failure
566 o 3-4 shift solenoid circuit failure (A4LD)
569 orc Auxiliary Canister Purge (AUX-CANP) circuit failure
617 orc 1-2 shift error
618 orc 2-3 shift error
619 orc 3-4 shift error
621 o Shift Solenoid 1 (SS1) circuit failure
622 o Shift Solenoid 2 (SS2) circuit failure
624 orc Electronic Pressure Control (EPC) circuit failure
625 orc Electronic Pressure Control (EPC) driver open in PCM 
626 o Coast Clutch Solenoid (CCS) circuit failure
628 rc Excessive converter clutch slippage
629 o Torque Converter Clutch (TCC) solenoid circuit failure 
631 orc Transmission Control Indicator Lamp (TCIL) circuit failure 
632 r Transmission Control Switch (TCS) circuit did not change states (operator error)
633 o 4x4L (Low) switch closed (operator error)
634 orc Transmission Range (TR) voltage higher or lower than expected
636 orc Transmission Fluid Temp (TFT) higher or lower than expected 
637 orc Transmission Fluid Temp (TFT) sensor circuit above maximum voltage/-40°F indicated
638 orc Transmission Fluid Temp (TFT) sensor circuit below minimum voltage/290°F indicated
639 c Insufficient input from Transmission Speed Sensor (TSS) 
641 o Shift Solenoid 3 (SS3) circuit failure
643 o Coast Clutch Solenoid (CCS) circuit failure
652 orc Torque Converter Clutch (TCC) solenoid circuit failure 
654 or Transmission Range (TR) sensor indicating not in PARK during Self-Test (operator error or MLPS failed or shift linkage out of adjustment)
655 or Transmission Range (TR) sensor indicating not in NEUTRAL during Self-Test (operator error or MLPS failed or shift linkage out of adjustment)
656 c Torque Converter Clutch slippage error 
657 orc Transmission Fluid Temperature (TFT) over temperature 
667 orc Transmission Range (TR) circuit voltage below minimum voltage
668 orc Transmission Range (TR) circuit voltage above maximum voltage 
691 orc 4X4 Low switch open or short circuit 
692 rc Transmission state does not match calculated ratio
998 r Hard fault present, FMEM mode
NO CODES Unable to initiate Self-Test or unable to output Self-Test codes (replace MIL bulb, inspect PC board inside EEC, read TSB below)

[url=http://www.fourdoorbronco.com/board/showthread.php?t=5226]Automotive Terms & Abbreviations[/url]

__________________________________________

TSB 92-24-03 Explanation of 3-Digit Codes & MIL

Publication Date: NOVEMBER 18, 1992 

FORD: 1991-93 CROWN VICTORIA, ESCORT, MUSTANG, PROBE, TAURUS, TEMPO, THUNDERBIRD
LINCOLN-MERCURY: 1991-92 MARK VII
1991-93 CONTINENTAL, COUGAR, GRAND MARQUIS, SABLE, TOPAZ, TOWN CAR, TRACER
1993 MARK VIII
LIGHT TRUCK: 1991-93 AEROSTAR, BRONCO, ECONOLINE, EXPLORER, F SUPER DUTY, F-150-350 SERIES, RANGER

ISSUE: Occasionally, there are reports of the Malfunction Indicator Lamp (MIL) "Check Engine" Lamp (CEL) or "Service Engine Soon" (SES) lamp being lit with no Self-Test codes in Continuous Memory. An explanation of three digit EEC IV Self-Test Codes has been developed along with reasons for the MIL lamp being lit with no accompanying Continuous Memory Self-Test codes.

ACTION: Refer to the following explanation of three digit EEC IV Self Test Codes to determine why the MIL lamp is sometimes lit with no accompanying Continuous Memory Self-Test codes.


OVERVIEW OF THREE DIGIT EEC IV SELF-TEST CODES

Ford went from two digit to three digit EEC IV Self-Test codes in 1991 to service the increasing number of service codes required to support various government On-Board Diagnostic (OBD) regulations. The phase-in from two digit to three digit codes started in the 1991 model year and is largely complete except for some medium/heavy trucks that will retain two digit codes through the 1994 model year.

MIL LAMP ACTIVATION

Following is a list of reasons why a technician may see the MIL lamp lit with no accompanying Continuous Memory Self-Test codes.

1) Technician Not Familiar With Self-Test Code Output
There are two types of EEC Self-Tests, Key On Engine Off (KOEO) and Key On Engine Running (KOER). While both of these will test for various "hard faults" that are present when the test is run, the processor continuously monitors various operating parameters whenever the engine is running. If the processor detects a problem, it will store a "Continuous Memory" code and light the MIL. These Continuous Memory codes are put out during KOEO Self-Test after any codes associated with hard faults are output.

Self-Test Codes are displayed by flashing the MIL. They are also output as voltage pulses on the Self-Test Output (STO) circuit in the Self-Test connector. In either Self-Test mode, all codes are output twice and in KOEO, the hard fault codes are separated from the Continuous Memory codes by a "separator" pulse.

A technician that is unfamiliar with the EEC Self-Test can mistakenly believe that continuous Memory codes are not present when they really are. He may run KOER Self-Test and get a pass code (lll) and not realize that KOEO Self-Test must be run to receive any Continuous Memory codes. He may run KOEO Self-Test while counting MIL flashes and misinterpret the repeated hard fault pass code (lll) to mean that Continuous Memory does not contain any codes.

2) Inadvertent Erasure Of Continuous Memory Self-Test Codes
Continuous Memory Self-Test codes are erased by ungrounding STI before KOEO Self-Test is complete and all KOEO and Continuous Memory codes have been displayed. It is possible to inadvertently erase Continuous Memory codes by ungrounding STI without realizing that KOEO Self-Test is not complete or the processor has not finished displaying all the codes.

The EEC Self-Test codes are not only used by service technicians, they are used as a final system test in the assembly plants. To make this test as efficient as possible, Self-Test codes are output as a very fast, short pulsewidth signal before the codes are displayed by the flashing MIL. These "FAST" codes can only be interpreted by end-of-line equipment or code-reading testers like Ford's Self-Test Automatic Readout (STAR) testers.

The EEC IV processor puts out both 2-digit and 3-digit Self-Test codes in both formats, "FAST" pulsewidth mode and "SLOW" pulsewidth mode. While all "STAR" type testers display 2-digit codes, the original STAR tester cannot display 3-digit service codes. If the STAR tester is used on 3-digit service code applications, the display will be blank but the tester will beep. The beeps can be counted to determine service codes. The SUPER STAR II tester will only display 3-digit service codes in "FAST" code mode. If slow code mode is used on 3-digit service code applications, the display will be blank but the tester will beep. The beeps can be counted to determine service codes. For more information on running Self-Test, refer to the "EEC IV Quick Test Procedures and Appendix" section of the Powertrain Control/Emissions Diagnosis Service Manual.

Since certain STAR testers are capable of reading and displaying fast codes before the slow codes are finished being output on the MIL, a technician can assume that since he sees codes displayed, he can unground STI and move on. If he ungrounds STI before all slow codes are output, Continuous Memory will be erased and could put out a pass code (ll/lll) the next time KOEO Self-Test is run. The technician may also realize that his tester is in "SLOW" mode after he has initiated the KOEO test and stop the test to change tester settings. Another possibility is that another person, a vehicle owner or another technician, could have erased the codes before the technician reporting the situation has run Self-Test. In any of these situations, the vehicle must be driven until the Continuous Memory codes are reset.

3) The Concern That Set The Continuous Memory Code Is No Longer Present
The EEC processor will erase a Continuous Memory code if the concern that caused it has not been present for 40 or 80 warm-up cycles, depending on the vehicle. A warm-up cycle occurs when the vehicle is started with the coolant temperature below 120° F (49° C) and then shutdown with the coolant temperature above 150° F (66° C). If a vehicle is brought in for service with a MIL complaint and the vehicle is driven or otherwise allowed to warm-up before Self-Test is run, the code may be cleared before the technician tests it.

4) Grounded STO/MIL Circuit
The processor controls the MIL by grounding the STO/MIL circuit (Pin 17). If this circuit shorts to ground, whether the processor is controlling it or not, the MIL will be lit. Starting in 1991, if the processor has lit the MIL, it will hold it on for a minimum of 10 seconds. If the MIL flashes quickly, the concern is probably the STO/MIL circuit shorting intermittently to ground.

5) Engine Running In HLOS
The EEC processor will enter Hardware Limited Operation Strategy (HLOS) if it detects a problem that could cause further damage to the system. Under HLOS, the processor modifies its operating strategy so that certain functions are disabled but the vehicle can be safely driven in for service. If the vehicle is in HLOS, Continuous Memory codes will not be set and Self-Test cannot be initiated. However, Continuous codes that were set before the processor entered HLOS will be retained.

6) Misinterpretation Of MIL Bulb Check
The MIL will light as a bulb check if the key is on and the engine is not running. If the engine is running and stalls or stops for any reason with the key on, the MIL will be lit and no Continuous Memory codes will be set. When the key is first turned on, the MIL will stay lit briefly after the engine is started as part of the bulb check feature.

7) MIL Flashes During Self-Test
The circuit that controls the MIL is also the Self-Test Output (STO) circuit that goes to the Self-Test connector. The MIL will flash during Self-Test as the STO circuit is cycled on and off. This is normal and no Continuous codes are set.

8 ) Processor KAM Is Erased Or Fails
The Keep Alive Memory (KAM) within the processor must always have voltage supplied to it. This voltage is supplied by the Keep Alive Power (KAPWR) circuit (Pin 1) that connects directly to the battery. KAM contains adaptive parameter tables that allow the processor to adapt to different operating requirements. It also contains the Continuous Memory codes. Continuous Memory codes will be erased any time KAPWR is disconnected (i.e. battery disconnected, processor disconnected, breakout box installed, open in the wire, etc.). If KAM fails within the processor, all Continuous codes will also be erased.

9) Damaged STAR Tester
A damaged STAR tester can produce erroneous code output or accidentally erase Continuous Memory.

10) KOEO Processor RAM Test Failed
The processor's Random Access Memory (RAM) is tested during KOEO Self-Test. If the processor's RAM has failed, the MIL will light and no codes are output.

11) Intermittent VSS Fault Detected In Wiggle Mode
If in wiggle mode (STI grounded) and an intermittent Vehicle Speed Sensor (VSS) fault is detected, the MIL can be lit momentarily. If the VSS signal returns to normal, the associated code is erased. In normal operation, the VSS will not light the MIL.

12) IDM Pulsewidth Not Recognized By Processor (EDIS Vehicles)
EDIS vehicles can have the MIL on with no Continuous codes if the processor does not recognize the Ignition Diagnostic Monitor (IDM) pulsewidth. In this case, coil pack failure codes may not be set since the fault filters can be erased before they reach the threshold that sets the code.

13) Intermittent Ignition System Fault
Vehicles with a Cylinder Identification (CID) sensor can light the MIL with no Continuous codes present if an intermittent ignition system fault is present long enough to activate the MIL and then goes away. The CID sensor can indicate that the fault was momentary and clear the coil pack faults but the CID fault may not register if the fault goes away fast enough.

14) Intermittent Open STI Circuit
If the Self-Test Input (STI) circuit opened during KOEO Self-Test or code output, Continuous Memory would be cleared.

15) Power Lost To EEC Processor
On some applications, the processor can lose power while the MIL stays powered. The MIL can light if a ground path is present through the processor.

16) Other Warning Lamps Mistaken For MIL
The MIL can sometimes be confused with other warning lamps like the amber Air Bag lamp if they are located near each other in the dash panel.

17) Development Testing Or Wrong Processor Released To Production
The MIL can be lit without Continuous codes during testing or if the wrong processor is installed.

SUPERSEDES: 92-4-4
WARRANTY STATUS: INFORMATION ONLY

---------------------------------------------------------------------------

TSB 88-05-07 MIL Introduction 

Publication Date: MARCH 2, 1988

FORD: 1988 ALL CAR LINES
LINCOLN-MERCURY: 1988 ALL CAR LINES
MERKUR: 1988 ALL CAR LINES
LIGHT TRUCK: 1988 ALL LIGHT TRUCK LINES

ISSUE: The Malfunction Indicator Light (MIL) is a new feature that has been added to 1988 vehicles. Vehicle applications follow. The MIL (Check Engine Light/CEL) is active when the engine system requires service. An explanation of how and when the Malfunction Indicator Light (MIL) operates may need to be explained to some vehicle owners.

ACTION: Use the following service information to explain the operation of the Malfunction Indicator Light (MIL) to resolve customer concerns.

NOTE: IT IS NOT NECESSARY TO IMMEDIATELY TURN OFF THE ENGINE OR HAVE THE VEHICLE TOWED WHEN THE "CHECK ENGINE" (MIL) LIGHT COMES ON.

Vehicles Equipped with EEC IV
The CHECK ENGINE light will come on while engine is operating in Failure Mode Effects Management (FMEM) or Hardware Limited Operation Strategy (HLOS) modes. The light will stay on as long as the fault causing it is present.

In FMEM mode, the computer is receiving a sensor signal that is outside the limits set by the calibration strategy. In this mode, the computer uses an alternate strategy to maintain reasonable vehicle operation in spite of the fault. The following chart lists the system faults which will turn on the CHECK ENGINE light in this mode. The error code associated with this system fault is stored in Keep Alive Memory (KAM). If the fault is no longer present, the light will turn off and vehicle will return to normal vehicle strategy. The error code stored when the light was on was not erased. This code is one of the continuous error codes and can be accessed by running the KOEO self-test.

HLOS mode is used when the system fault(s) is too extreme for the FMEM mode to handle. In HLOS mode, all software operations have stopped and the computer is running on hardware control only. The default strategy for this mode has a minimal calibration just to allow the vehicle to operate until it can be serviced.
NOTE: IN HLOS MODE YOU WILL NOT GET ERROR CODES.

The MIL light is turned on as a bulb check when the ignition key is first turned "ON". The EEC IV computer turns off the bulb as soon as it receives the PIP (crank) signal. If the light stays on during cranking, the computer is not receiving the PIP signal.

To service a MIL concern, use the appropriate Engine/Emission Diagnosis Shop Manual. If the vehicle has no drive problems, the MIL is on, and no codes are found in memory, follow diagnostics by symptom in the Engine/Emission Diagnosis Shop Manual.

Non-EEC IV Vehicles
The Malfunction Indicator Light (MIL) alerts the customer that 60,000 mile emission system maintained is required. To service a MIL concern on a non-EEC IV vehicle, refer to the Engine/Emission Diagnostic Shop Manual.

OTHER APPLICABLE ARTICLES: NONE
WARRANTY STATUS: INFORMATION ONLY
dlc-eeciv.jpg | Hits: 79357 | Posted on: 9/18/05 | View original size (35.1 KB)

Diagnostic Link Connectors for EEC-IV processors ('84-95).
'84-86 (red) located on R wheelwell near starter relay.
'87-95 (black or gray) located under L hood hinge under EEC TEST cover. (WPT-743 & WPT-352)
'94-96 Bronco - do not confuse with RED 4WABS connector also under L hood hinge

'96-up use OBD-II, and this DLC:
.

Connect FP Relay (terminal A) to any ground (like terminal E) to force the fuel pump(s) on when the key is in RUN.

.

Pins D & F are a primitive SCP bus, but on these old vehicles, nothing else was networked in.

Connect pin 1 (209 W/Pu) to any ground (like terminal E) with any jumper wire (like a paperclip) to trigger diagnostic modes. (See the NEXT diagram.) Consult the 7th post on this page for the compete procedure to pull codes & trigger all test modes. If the CEL is burned out, connect CEL (C) to a 12V test light, and the light's other terminal to a 12V source on the same vehicle.

To hardwire a self-test switch in the dash, see:


Automotive Terms & Abbreviations
EEC-IV DTC definition list
Ryan's page similar to this one

No matter what code you get, DON'T PICK THE NAME OF A PART OUT of the code definition - read the WHOLE definition, and then confirm the condition it indicates. If the condition doesn't exist, clear the code and see how long it takes to re-set that code. If the condition DOES exist, learn about the system to identify EVERY possible cause of the condition. For instance: if the EVP doesn't indicate the EGR is opening, that doesn't mean to replace either of them. It could simply be a vacuum leak in one of the lines, or the reservoir.

If spurious or false codes are delivered, remove the EEC & inspect its PC board for leaking capacitors.



For voltage faults &/or contradictory faults, repair the battery terminals first:



Conditions: o = Key On Engine Off (KOEO), r = Engine Running (KOER), c = Continuous Memory
NO CODES Unable to initiate Self-Test or unable to output Self-Test codes (replace MIL bulb, inspect PC board inside EEC, read TSB below)
---------2-digit codes used until 1991---------
11 orc System PASS
12 r Cannot control rpm during Self-Test high rpm check
13 r Cannot control rpm during Self-Test low rpm check
14 c PIP circuit failure (gas); tach sensor failure (diesel)
15 o EEC processor Read Only Memory (ROM) test failed
15 c EEC processor Keep Alive Memory (KAM) test failed
18 r SPOUT circuit open
18 c Loss of IDM input to processor/SPOUT circuit grounded
19 o Failure in EEC processor internal voltage
21 or Engine Cooling Temperature (ECT) sensor out of Self-Test range (engine not warmed up before test)
22 orc Manifold Absolute Pressure (MAP) sensor out of Self-Test range
23 orc Throttle Position (TP) sensor out of Self-Test range
24 or Air Charge Temperature (ACT) sensor out of Self-Test range
25 r Knock not sensed during Dynamic Response Test (operator error)
26 or Transmission Fluid Temp (TFT) out of Self-Test range (engine not warmed up before test)
29 c Insufficient Vehicle Speed Signal (VSS) input
31 orc EVP circuit below minimum voltage
32 orc EVP voltage below closed limit
33 rc EGR valve opening not detected (no change in EVP when EVR activated)
34 orc EVP voltage above closed limit
35 orc EVP circuit above maximum voltage
41 r HEGO sensor circuit indicates system lean
41 c No HEGO switching detected
42 r HEGO sensor circuit indicates system rich
43 c Throttle Position (TP) sensor below idle spec
44 r Thermactor air system inoperative (TAB or TAD open circuit)
45 r Thermactor air upstream/misdirected during KOER
46 r Thermactor air not bypassed during KOER
47 o 4x4 switch closed during test (operator error)
49 c 1-2 Shift error
51 oc ECT indicated -40C (-40F)/circuit open
52 o Power Steering Pressure Switch (PSPS) circuit open
52 r PSPS circuit did not change states during Dynamic Response Test (operator error)
53 oc TP above maximum voltage
54 oc ACT indicated -40C (-40F)/circuit open
56 oc Transmission Fluid Temp (TFT) indicated -40C (-40F)/circuit open
59 c 2-3 Shift error
61 oc ECT indicated 123C (254F)/circuit grounded
62 c Torque Converter Clutch error
63 oc TP circuit below minimum voltage
64 oc ACT indicated 123C (254F)/circuit grounded
65 r Transmission Control Switch (TCS) circuit did not change states during Dynamic Response Test (operator error)
66 oc Transmission Fluid Temp (TFT) indicated 143C (290F)/circuit grounded
67 o Neutral Drive Switch (NDS) circuit open; A/C or Defrost on (Manual) during test (operator error)
68 c Transmission Fluid Temp (TFT) transmission over temp (over-heated)
69 c 3-4 Shift error
72 r Insufficient MAP change during Dynamic Response Test (operator error)
73 r Insufficient TP change during Dynamic Response Test (operator error)
74 rc Brake On/Off (BOO) circuit open or not actuated during Self-Test (operator error)
77 r Operator error during Dynamic Response Test
81 o Air Management 2 (AM2/TAD) circuit failure
82 o Air Management 1 (AM1/TAB) circuit failure
84 o EGR Vacuum Regulator (EVR) circuit failure
85 o Canister Purge (CANP) circuit failure
87 oc Primary fuel pump circuit failure
91 o Shift Solenoid 1 (SS1) circuit failure
92 o Shift Solenoid 2 (SS2) circuit failure
93 o Coast Clutch Solenoid (CCS) circuit failure
94 o Torque Converter Clutch (TCC) solenoid circuit failure
95 oc Fuel Pump circuit open - EEC processor to motor ground (fuel pump unplugged or wiring damage)
96 oc Fuel Pump circuit open - battery to EEC processor (inertia switch tripped or FP relay failed)
97 o Transmission Control Indicator Lamp (TCIL) circuit failure
98 r Hard fault present
99 oc Electronic Pressure Control (EPC) circuit failure
2-digit codes------------1991------------3-digit codes
111 orc System PASS
112 oc ACT indicated 123C (254F)/circuit grounded
113 oc ACT indicated -40C (-40F)/circuit open
114 or Air Charge Temperature (ACT) Sensor out of Self-Test range
116 or Engine Cooling Temperature (ECT) Sensor out of Self-Test range (engine not warmed up before test)
117 oc ECT indicated 123C (254F)/circuit grounded
118 oc ECT indicated -40C (-40F)/circuit open
121 orc Throttle Position (TP) Sensor out of Self-Test range
121 rc Throttle position voltage inconsistent with MAF sensor (vacuum leak downstream of MAF)
122 oc TP circuit below minimum voltage
123 oc TP above maximum voltage
124 rc Throttle Position (TP) sensor voltage higher than expected
125 rc Throttle Position (TP) sensor voltage lower than expected
126 orc Manifold Absolute Pressure (MAP) Sensor out of Self-Test range
128 c MAP vacuum circuit failure
129 r Insufficient MAP change during Dynamic Response Test (operator error)
136 c System indicates lean (Bank #2)
137 r System indicates lean (Bank #2)
157 orc Mass Air Flow (MAF) sensor circuit below minimum voltage
158 orc Mass Air Flow (MAF) sensor circuit above maximum voltage
159 orc Mass Air Flow (MAF) sensor circuit voltage higher or lower than expected
167 r Insufficient TP change during Dynamic Response Test (operator error)
171 c Fuel system at adaptive limits, Oxygen Sensor (HEGO) unable to switch, Bank 1
172 rc Lack of Oxygen Sensor (HEGO) switches, indicates lean, Bank 1
173 rc Lack of Oxygen Sensor (HEGO) switches, indicates rich, Bank 1
175 c Fuel system at adaptive limits, Oxygen Sensor (HEGO) unable to switch, Bank 2
176 rc Lack of Oxygen Sensor (HEGO) switches, indicates lean, Bank 2
177 rc Lack of Oxygen Sensor (HEGO) switches, indicates rich, Bank 2
179 c Fuel system at lean adaptive limit at part throttle, system rich, Bank 1
181 c Fuel system at rich adaptive limit at part throttle, system lean, Bank 1
184 orc Mass Air Flow (MAF) sensor voltage higher than expected
185 orc Mass Air Flow (MAF) sensor voltage lower than expected
186 orc Injector pulsewidth higher than expected (with BARO/MAP sensor)
186 orc Injector pulsewidth higher or mass air flow lower than expected (without BARO/MAP sensor)
187 orc Injector pulsewidth lower than expected (with BARO/MAP sensor)
187 orc Injector pulsewidth lower or mass air flow higher than expected (without BARO/MAP sensor)
188 c Fuel system at lean adaptive limit at part throttle, system rich (Bank #2)
189 c Fuel system at rich adaptive limit at part throttle, system lean (Bank #2)
211 c PIP circuit failure
212 c Loss of IDM input to processor/SPOUT circuit grounded
213 r SPOUT circuit open
214 orc Cylinder Identification (CID/CPS) circuit failure
215 orc PCM detected coil 1 primary circuit failure (EI/EDIS)
216 orc PCM detected coil 2 primary circuit failure (EI/EDIS)
217 orc PCM detected coil 3 primary circuit failure (EI/EDIS)
218 orc Loss of Ignition Diagnostic Monitor (IDM) signal-left side (dual plug EI/EDIS)
222 orc Loss of Ignition Diagnostic Monitor (IDM) signal-right side (dual plug EI/EDIS)
223 orc Loss of Dual Plug Inhibit (DPI) control (dual plug EI/EDIS)
224 orc PCM detected coil 1, 2, 3 or 4 primary circuit failure (dual plug EI/EDIS)
225 r Knock not sensed during Dynamic Response Test (operator error)
226 orc Ignition Diagnostic Monitor (IDM) signal not received (EI/EDIS)
232 orc PCM detected coil 1, 2, 3 or 4 primary circuit failure (EI/EDIS)
311 r Thermactor air system inoperative (Bank #1 w/dual HO2S)
312 r Thermactor air upstream/misdirected
313 r Thermactor air not bypassed
327 orc EVP circuit below minimum voltage
328 orc EVP voltage below closed limit
332 rc EGR valve opening not detected
334 orc EVP voltage above closed limit
334 orc EVP closed voltage higher than expected
335 o EGR (PFE) sensor voltage higher or lower than expected
336 orc Exhaust pressure high; PFE/DPFE circuit voltage higher than expected
337 orc EGR (EVP/PFE) circuit above maximum voltage
341 orc Octane adjust service pin open
411 r Cannot control rpm during low rpm check
412 r Cannot control rpm during high rpm check
452 c Insufficient Vehicle Speed Signal (VSS) input
511 o EEC processor Read Only Memory (ROM) test failed
512 c EEC processor Keep Alive Memory (KAM) test failed
513 o Failure in EEC processor internal voltage
519 o Power Steering Pressure (PSP) switch circuit open
521 r Power Steering Pressure (PSP) switch circuit did not change states (operator error)
522 o Vehicle not in PARK or NEUTRAL during KOEO test (operator error)
528 c Clutch switch circuit failure
536 r Brake On/Off (BOO) circuit failure/not actuated during Dynamic Response Test (operator error)
538 r Insufficient RPM change during Dynamic Response Test (operator error)
538 r Invalid cylinder balance test due to throttle movement during test (operator error)
538 r Invalid cylinder balance test due to CID circuit failure
539 or A/C on/Defrost on during test (operator error)
542 oc Fuel Pump circuit open - EEC processor to pump motor (no ground with FP relay OFF)
543 oc Fuel Pump circuit open - battery to EEC processor (no power with FP relay ON)
551 o Idle Air Control (IAC) circuit failure
552 o Air Management 1 (AM1/TAB) circuit failure
553 o Air Management 2 (AM2/TAD) circuit failure
556 oc Primary fuel pump circuit failure
558 o EGR Vacuum Regulator (EVR) circuit failure
565 o Canister Purge (CANP) circuit failure
566 o 3-4 shift solenoid circuit failure (A4LD)
569 orc Auxiliary Canister Purge (AUX-CANP) circuit failure
617 orc 1-2 shift error
618 orc 2-3 shift error
619 orc 3-4 shift error
621 o Shift Solenoid 1 (SS1) circuit failure
622 o Shift Solenoid 2 (SS2) circuit failure
624 orc Electronic Pressure Control (EPC) circuit failure
625 orc Electronic Pressure Control (EPC) driver open in PCM
626 o Coast Clutch Solenoid (CCS) circuit failure
628 rc Excessive converter clutch slippage
629 o Torque Converter Clutch (TCC) solenoid circuit failure
631 orc Transmission Control Indicator Lamp (TCIL) circuit failure
632 r Transmission Control Switch (TCS) circuit did not change states (operator error)
633 o 4x4L (Low) switch closed (operator error)
634 orc Transmission Range (TR) voltage higher or lower than expected
636 orc Transmission Fluid Temp (TFT) higher or lower than expected
637 orc Transmission Fluid Temp (TFT) sensor circuit above maximum voltage/-40F indicated
638 orc Transmission Fluid Temp (TFT) sensor circuit below minimum voltage/290F indicated
639 c Insufficient input from Transmission Speed Sensor (TSS)
641 o Shift Solenoid 3 (SS3) circuit failure
643 o Coast Clutch Solenoid (CCS) circuit failure
652 orc Torque Converter Clutch (TCC) solenoid circuit failure
654 or Transmission Range (TR) sensor indicating not in PARK during Self-Test (operator error or MLPS failed or shift linkage out of adjustment)
655 or Transmission Range (TR) sensor indicating not in NEUTRAL during Self-Test (operator error or MLPS failed or shift linkage out of adjustment)
656 c Torque Converter Clutch slippage error
657 orc Transmission Fluid Temperature (TFT) over temperature
667 orc Transmission Range (TR) circuit voltage below minimum voltage
668 orc Transmission Range (TR) circuit voltage above maximum voltage
691 orc 4X4 Low switch open or short circuit
692 rc Transmission state does not match calculated ratio
998 r Hard fault present, FMEM mode
NO CODES Unable to initiate Self-Test or unable to output Self-Test codes (replace MIL bulb, inspect PC board inside EEC, read TSB below)

Automotive Terms & Abbreviations

__________________________________________

TSB 92-24-03 Explanation of 3-Digit Codes & MIL

Publication Date: NOVEMBER 18, 1992

FORD: 1991-93 CROWN VICTORIA, ESCORT, MUSTANG, PROBE, TAURUS, TEMPO, THUNDERBIRD
LINCOLN-MERCURY: 1991-92 MARK VII
1991-93 CONTINENTAL, COUGAR, GRAND MARQUIS, SABLE, TOPAZ, TOWN CAR, TRACER
1993 MARK VIII
LIGHT TRUCK: 1991-93 AEROSTAR, BRONCO, ECONOLINE, EXPLORER, F SUPER DUTY, F-150-350 SERIES, RANGER

ISSUE: Occasionally, there are reports of the Malfunction Indicator Lamp (MIL) "Check Engine" Lamp (CEL) or "Service Engine Soon" (SES) lamp being lit with no Self-Test codes in Continuous Memory. An explanation of three digit EEC IV Self-Test Codes has been developed along with reasons for the MIL lamp being lit with no accompanying Continuous Memory Self-Test codes.

ACTION: Refer to the following explanation of three digit EEC IV Self Test Codes to determine why the MIL lamp is sometimes lit with no accompanying Continuous Memory Self-Test codes.


OVERVIEW OF THREE DIGIT EEC IV SELF-TEST CODES

Ford went from two digit to three digit EEC IV Self-Test codes in 1991 to service the increasing number of service codes required to support various government On-Board Diagnostic (OBD) regulations. The phase-in from two digit to three digit codes started in the 1991 model year and is largely complete except for some medium/heavy trucks that will retain two digit codes through the 1994 model year.

MIL LAMP ACTIVATION

Following is a list of reasons why a technician may see the MIL lamp lit with no accompanying Continuous Memory Self-Test codes.

1) Technician Not Familiar With Self-Test Code Output
There are two types of EEC Self-Tests, Key On Engine Off (KOEO) and Key On Engine Running (KOER). While both of these will test for various "hard faults" that are present when the test is run, the processor continuously monitors various operating parameters whenever the engine is running. If the processor detects a problem, it will store a "Continuous Memory" code and light the MIL. These Continuous Memory codes are put out during KOEO Self-Test after any codes associated with hard faults are output.

Self-Test Codes are displayed by flashing the MIL. They are also output as voltage pulses on the Self-Test Output (STO) circuit in the Self-Test connector. In either Self-Test mode, all codes are output twice and in KOEO, the hard fault codes are separated from the Continuous Memory codes by a "separator" pulse.

A technician that is unfamiliar with the EEC Self-Test can mistakenly believe that continuous Memory codes are not present when they really are. He may run KOER Self-Test and get a pass code (lll) and not realize that KOEO Self-Test must be run to receive any Continuous Memory codes. He may run KOEO Self-Test while counting MIL flashes and misinterpret the repeated hard fault pass code (lll) to mean that Continuous Memory does not contain any codes.

2) Inadvertent Erasure Of Continuous Memory Self-Test Codes
Continuous Memory Self-Test codes are erased by ungrounding STI before KOEO Self-Test is complete and all KOEO and Continuous Memory codes have been displayed. It is possible to inadvertently erase Continuous Memory codes by ungrounding STI without realizing that KOEO Self-Test is not complete or the processor has not finished displaying all the codes.

The EEC Self-Test codes are not only used by service technicians, they are used as a final system test in the assembly plants. To make this test as efficient as possible, Self-Test codes are output as a very fast, short pulsewidth signal before the codes are displayed by the flashing MIL. These "FAST" codes can only be interpreted by end-of-line equipment or code-reading testers like Ford's Self-Test Automatic Readout (STAR) testers.

The EEC IV processor puts out both 2-digit and 3-digit Self-Test codes in both formats, "FAST" pulsewidth mode and "SLOW" pulsewidth mode. While all "STAR" type testers display 2-digit codes, the original STAR tester cannot display 3-digit service codes. If the STAR tester is used on 3-digit service code applications, the display will be blank but the tester will beep. The beeps can be counted to determine service codes. The SUPER STAR II tester will only display 3-digit service codes in "FAST" code mode. If slow code mode is used on 3-digit service code applications, the display will be blank but the tester will beep. The beeps can be counted to determine service codes. For more information on running Self-Test, refer to the "EEC IV Quick Test Procedures and Appendix" section of the Powertrain Control/Emissions Diagnosis Service Manual.

Since certain STAR testers are capable of reading and displaying fast codes before the slow codes are finished being output on the MIL, a technician can assume that since he sees codes displayed, he can unground STI and move on. If he ungrounds STI before all slow codes are output, Continuous Memory will be erased and could put out a pass code (ll/lll) the next time KOEO Self-Test is run. The technician may also realize that his tester is in "SLOW" mode after he has initiated the KOEO test and stop the test to change tester settings. Another possibility is that another person, a vehicle owner or another technician, could have erased the codes before the technician reporting the situation has run Self-Test. In any of these situations, the vehicle must be driven until the Continuous Memory codes are reset.

3) The Concern That Set The Continuous Memory Code Is No Longer Present
The EEC processor will erase a Continuous Memory code if the concern that caused it has not been present for 40 or 80 warm-up cycles, depending on the vehicle. A warm-up cycle occurs when the vehicle is started with the coolant temperature below 120 F (49 C) and then shutdown with the coolant temperature above 150 F (66 C). If a vehicle is brought in for service with a MIL complaint and the vehicle is driven or otherwise allowed to warm-up before Self-Test is run, the code may be cleared before the technician tests it.

4) Grounded STO/MIL Circuit
The processor controls the MIL by grounding the STO/MIL circuit (Pin 17). If this circuit shorts to ground, whether the processor is controlling it or not, the MIL will be lit. Starting in 1991, if the processor has lit the MIL, it will hold it on for a minimum of 10 seconds. If the MIL flashes quickly, the concern is probably the STO/MIL circuit shorting intermittently to ground.

5) Engine Running In HLOS
The EEC processor will enter Hardware Limited Operation Strategy (HLOS) if it detects a problem that could cause further damage to the system. Under HLOS, the processor modifies its operating strategy so that certain functions are disabled but the vehicle can be safely driven in for service. If the vehicle is in HLOS, Continuous Memory codes will not be set and Self-Test cannot be initiated. However, Continuous codes that were set before the processor entered HLOS will be retained.

6) Misinterpretation Of MIL Bulb Check
The MIL will light as a bulb check if the key is on and the engine is not running. If the engine is running and stalls or stops for any reason with the key on, the MIL will be lit and no Continuous Memory codes will be set. When the key is first turned on, the MIL will stay lit briefly after the engine is started as part of the bulb check feature.

7) MIL Flashes During Self-Test
The circuit that controls the MIL is also the Self-Test Output (STO) circuit that goes to the Self-Test connector. The MIL will flash during Self-Test as the STO circuit is cycled on and off. This is normal and no Continuous codes are set.

8 ) Processor KAM Is Erased Or Fails
The Keep Alive Memory (KAM) within the processor must always have voltage supplied to it. This voltage is supplied by the Keep Alive Power (KAPWR) circuit (Pin 1) that connects directly to the battery. KAM contains adaptive parameter tables that allow the processor to adapt to different operating requirements. It also contains the Continuous Memory codes. Continuous Memory codes will be erased any time KAPWR is disconnected (i.e. battery disconnected, processor disconnected, breakout box installed, open in the wire, etc.). If KAM fails within the processor, all Continuous codes will also be erased.

9) Damaged STAR Tester
A damaged STAR tester can produce erroneous code output or accidentally erase Continuous Memory.

10) KOEO Processor RAM Test Failed
The processor's Random Access Memory (RAM) is tested during KOEO Self-Test. If the processor's RAM has failed, the MIL will light and no codes are output.

11) Intermittent VSS Fault Detected In Wiggle Mode
If in wiggle mode (STI grounded) and an intermittent Vehicle Speed Sensor (VSS) fault is detected, the MIL can be lit momentarily. If the VSS signal returns to normal, the associated code is erased. In normal operation, the VSS will not light the MIL.

12) IDM Pulsewidth Not Recognized By Processor (EDIS Vehicles)
EDIS vehicles can have the MIL on with no Continuous codes if the processor does not recognize the Ignition Diagnostic Monitor (IDM) pulsewidth. In this case, coil pack failure codes may not be set since the fault filters can be erased before they reach the threshold that sets the code.

13) Intermittent Ignition System Fault
Vehicles with a Cylinder Identification (CID) sensor can light the MIL with no Continuous codes present if an intermittent ignition system fault is present long enough to activate the MIL and then goes away. The CID sensor can indicate that the fault was momentary and clear the coil pack faults but the CID fault may not register if the fault goes away fast enough.

14) Intermittent Open STI Circuit
If the Self-Test Input (STI) circuit opened during KOEO Self-Test or code output, Continuous Memory would be cleared.

15) Power Lost To EEC Processor
On some applications, the processor can lose power while the MIL stays powered. The MIL can light if a ground path is present through the processor.

16) Other Warning Lamps Mistaken For MIL
The MIL can sometimes be confused with other warning lamps like the amber Air Bag lamp if they are located near each other in the dash panel.

17) Development Testing Or Wrong Processor Released To Production
The MIL can be lit without Continuous codes during testing or if the wrong processor is installed.

SUPERSEDES: 92-4-4
WARRANTY STATUS: INFORMATION ONLY

---------------------------------------------------------------------------

TSB 88-05-07 MIL Introduction

Publication Date: MARCH 2, 1988

FORD: 1988 ALL CAR LINES
LINCOLN-MERCURY: 1988 ALL CAR LINES
MERKUR: 1988 ALL CAR LINES
LIGHT TRUCK: 1988 ALL LIGHT TRUCK LINES

ISSUE: The Malfunction Indicator Light (MIL) is a new feature that has been added to 1988 vehicles. Vehicle applications follow. The MIL (Check Engine Light/CEL) is active when the engine system requires service. An explanation of how and when the Malfunction Indicator Light (MIL) operates may need to be explained to some vehicle owners.

ACTION: Use the following service information to explain the operation of the Malfunction Indicator Light (MIL) to resolve customer concerns.

NOTE: IT IS NOT NECESSARY TO IMMEDIATELY TURN OFF THE ENGINE OR HAVE THE VEHICLE TOWED WHEN THE "CHECK ENGINE" (MIL) LIGHT COMES ON.

Vehicles Equipped with EEC IV
The CHECK ENGINE light will come on while engine is operating in Failure Mode Effects Management (FMEM) or Hardware Limited Operation Strategy (HLOS) modes. The light will stay on as long as the fault causing it is present.

In FMEM mode, the computer is receiving a sensor signal that is outside the limits set by the calibration strategy. In this mode, the computer uses an alternate strategy to maintain reasonable vehicle operation in spite of the fault. The following chart lists the system faults which will turn on the CHECK ENGINE light in this mode. The error code associated with this system fault is stored in Keep Alive Memory (KAM). If the fault is no longer present, the light will turn off and vehicle will return to normal vehicle strategy. The error code stored when the light was on was not erased. This code is one of the continuous error codes and can be accessed by running the KOEO self-test.

HLOS mode is used when the system fault(s) is too extreme for the FMEM mode to handle. In HLOS mode, all software operations have stopped and the computer is running on hardware control only. The default strategy for this mode has a minimal calibration just to allow the vehicle to operate until it can be serviced.
NOTE: IN HLOS MODE YOU WILL NOT GET ERROR CODES.

The MIL light is turned on as a bulb check when the ignition key is first turned "ON". The EEC IV computer turns off the bulb as soon as it receives the PIP (crank) signal. If the light stays on during cranking, the computer is not receiving the PIP signal.

To service a MIL concern, use the appropriate Engine/Emission Diagnosis Shop Manual. If the vehicle has no drive problems, the MIL is on, and no codes are found in memory, follow diagnostics by symptom in the Engine/Emission Diagnosis Shop Manual.

Non-EEC IV Vehicles
The Malfunction Indicator Light (MIL) alerts the customer that 60,000 mile emission system maintained is required. To service a MIL concern on a non-EEC IV vehicle, refer to the Engine/Emission Diagnostic Shop Manual.

OTHER APPLICABLE ARTICLES: NONE
WARRANTY STATUS: INFORMATION ONLY
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