What fuse powers the Malfunction Indicator Lamp (MIL) circuit on a 1994 Bronco/F-Series 5.0L?

Fuse 17, a 10A fuse in the fuse panel (pages 13-3, 13-9), which is hot in START or RUN and feeds the MIL via wire 640 R/Y.

Why does the check engine light (MIL) come on before starting the engine?

Per the diagram note, the indicator lights with the ignition switch in ON prior to cranking and goes off when the engine starts. If a fault develops in the Engine Control System, the PCM turns the indicator on.

What does the clutch pedal position switch do on a manual-transmission 1994 Bronco/F-Series?

It prevents engine startup with the clutch pedal released. It receives 12V (START) on wire 480 P/Y at connector C261 and passes it out as wire 481 GY/Y when the switch is closed.

How are automatic transmissions handled in the clutch switch circuit?

Vehicles with E4OD, 4R70W, or C6 transmissions use a clutch pedal position switch jumper at C261 instead of a switch, connecting wire 480 P/Y to 481 GY/Y.

What wire carries the MIL signal to the PCM?

Wire 658 PK/LG runs from the MIL through connectors C251, C202, and C198 (VIP Data Link Connector) to PCM pin 17.

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1994 Ford Bronco/F-Series 5.0L Engine Controls Wiring Diagram - MIL & PCM Power

1994 Bronco/F-Series Engine Controls 5.0L wiring diagram, page 24-7

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Ford 1994 Bronco/F-Series 5.0L engine controls wiring diagram covering ignition switch, clutch pedal switches and PCM with color codes.

AI caption February 2007 · Photo 245 of 1902

This document is page 24-7 of a 1994 Ford Bronco/F-Series wiring diagram manual, covering Engine Controls for the 5.0L engine. It traces two power feeds into the Powertrain Control Module (PCM) circuit. The first, hot in START or RUN, comes from fuse 17 (10A) in the fuse panel through wire 640 R/Y and splice S215 to the Malfunction Indicator Lamp (MIL) in the instrument cluster, then via wire 658 PK/LG through connectors C251, C202, and C198 (VIP Data Link Connector) to PCM pin 17. A note explains the MIL lights with the ignition ON before cranking and is turned on by the PCM if a fault develops. The second feed, hot at all times, passes through the ignition switch (START) via wire 32 R/LB, splice S224, and wire 480 P/Y to the clutch pedal position switch (manual transmission) or jumpers (E4OD/4R70W and C6 automatics), then wire 481 GY/Y to PCM pin 30 (without E4OD/4R70W). The clutch switch prevents engine startup with the clutch pedal released. Also shown are 4R70W transmission wires 970 DG/W and 766 BK/LG (pins 5, 29) and A/C-heater wires 883 PK/LB and 348 P (pins 10, 43), with cross-references to power distribution, starting system, instrument cluster, and A/C pages.

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Frequently asked questions

What fuse powers the Malfunction Indicator Lamp (MIL) circuit on a 1994 Bronco/F-Series 5.0L?: Fuse 17, a 10A fuse in the fuse panel (pages 13-3, 13-9), which is hot in START or RUN and feeds the MIL via wire 640 R/Y.
Why does the check engine light (MIL) come on before starting the engine?: Per the diagram note, the indicator lights with the ignition switch in ON prior to cranking and goes off when the engine starts. If a fault develops in the Engine Control System, the PCM turns the indicator on.
What does the clutch pedal position switch do on a manual-transmission 1994 Bronco/F-Series?: It prevents engine startup with the clutch pedal released. It receives 12V (START) on wire 480 P/Y at connector C261 and passes it out as wire 481 GY/Y when the switch is closed.
How are automatic transmissions handled in the clutch switch circuit?: Vehicles with E4OD, 4R70W, or C6 transmissions use a clutch pedal position switch jumper at C261 instead of a switch, connecting wire 480 P/Y to 481 GY/Y.
What wire carries the MIL signal to the PCM?: Wire 658 PK/LG runs from the MIL through connectors C251, C202, and C198 (VIP Data Link Connector) to PCM pin 17.