What does code 543 mean on a 1991-95 Ford Bronco or F-series?

Code 543 indicates the Fuel Pump circuit is open between the battery and the EEC processor — no power with the fuel pump relay ON. Code 542 is the related fault: circuit open from the EEC processor to the pump motor (no ground with FP relay OFF).

What are the transmission shift solenoid codes on these trucks?

Code 621 is Shift Solenoid 1 (SS1) circuit failure, 622 is Shift Solenoid 2 (SS2) circuit failure, 641 is Shift Solenoid 3 (SS3) circuit failure, and 566 is the 3-4 shift solenoid circuit failure on the A4LD.

What do codes 654 and 655 indicate?

Code 654 means the Transmission Range (TR) sensor indicates the vehicle is not in PARK during Self-Test; code 655 means not in NEUTRAL. Either can be operator error, a failed MLPS, or shift linkage out of adjustment.

What wire colors are shown at the EEC-IV diagnostic connectors?

The diagram shows connector C198 (black) and C199 (gray) with circuits 915 (PK/LB), 914 (T/O), 658 (PK/LG), 359 (GY/R) linked to 209 (W/P), and 926 (LB/O).

What does code 637 versus 638 mean for transmission fluid temperature?

Code 637 means the TFT sensor circuit is above maximum voltage, indicating -40°F; code 638 means the circuit is below minimum voltage, indicating 290°F. Code 636 means TFT is higher or lower than expected, and 657 indicates over temperature.

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1991-95 Ford Bronco/F-Series EEC-IV 3-Digit DTC Codes 335-998 (Page 2)

1991-95 Bronco/F-series EEC-IV 3-digit diagnostic trouble code list with descriptions

3-Digit Diagnostic Trouble Codes (DTCs) for '90-95 EEC-IV Trucks (p.2 of 2) SEE THE PREVious PAGE...
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This document is page 2 of a two-page chart listing Ford EEC-IV 3-digit Diagnostic Trouble Codes (DTCs) for 1991-95 Bronco and F-series trucks. It covers codes 335 through 998, with each entry showing the code number, a three-character flag indicating the test mode in which the code appears (o = Key On Engine Off, r = Key On Engine Running, c = Continuous Memory), and a description of the fault. Codes cover EGR/PFE sensor faults, EEC processor memory failures (ROM/KAM), power steering pressure switch, clutch and brake switch circuits, fuel pump circuits, idle air control, air management, canister purge, and an extensive set of E4OD/A4LD transmission codes including shift solenoids (SS1-SS3), Electronic Pressure Control (EPC), Torque Converter Clutch (TCC), Transmission Range (TR) sensor, Transmission Fluid Temperature (TFT), and 4x4 Low switch faults. Several codes are noted as operator errors during self-test (e.g., 521, 522, 536, 632, 654, 655). An inset diagram shows the EEC-IV Data Link Connector (DLC) and VIP test connectors C198 (black) and C199 (gray), with circuit numbers and wire colors: 915 (PK/LB), 914 (T/O), 658 (PK/LG), 359 (GY/R), 209 (W/P), and 926 (LB/O). Useful for interpreting self-test codes retrieved during KOEO/KOER diagnostics.

This document covers 1991-1995, which may differ from this 1983 Ford Bronco.

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Frequently asked questions

What does code 543 mean on a 1991-95 Ford Bronco or F-series?: Code 543 indicates the Fuel Pump circuit is open between the battery and the EEC processor — no power with the fuel pump relay ON. Code 542 is the related fault: circuit open from the EEC processor to the pump motor (no ground with FP relay OFF).
What are the transmission shift solenoid codes on these trucks?: Code 621 is Shift Solenoid 1 (SS1) circuit failure, 622 is Shift Solenoid 2 (SS2) circuit failure, 641 is Shift Solenoid 3 (SS3) circuit failure, and 566 is the 3-4 shift solenoid circuit failure on the A4LD.
What do codes 654 and 655 indicate?: Code 654 means the Transmission Range (TR) sensor indicates the vehicle is not in PARK during Self-Test; code 655 means not in NEUTRAL. Either can be operator error, a failed MLPS, or shift linkage out of adjustment.
What wire colors are shown at the EEC-IV diagnostic connectors?: The diagram shows connector C198 (black) and C199 (gray) with circuits 915 (PK/LB), 914 (T/O), 658 (PK/LG), 359 (GY/R) linked to 209 (W/P), and 926 (LB/O).
What does code 637 versus 638 mean for transmission fluid temperature?: Code 637 means the TFT sensor circuit is above maximum voltage, indicating -40°F; code 638 means the circuit is below minimum voltage, indicating 290°F. Code 636 means TFT is higher or lower than expected, and 657 indicates over temperature.