Which fuse powers the Malfunction Indicator Lamp (MIL) circuit?

Fuse 17, a 10A fuse in the fuse panel (pages 13-3), hot in Start or Run, feeding circuit 640 R/Y.

Which fuse powers the LH heated oxygen sensor?

Fuse E, a 15A fuse in the engine compartment fuse box (pages 13-4), hot in Run, on circuit 298 P/O.

What wire color and PCM pin does the LH HO2S signal use?

The signal is on circuit 94 R/BK, passing through connectors C110F/C110M to PCM pin 43; the sensor ground is 57 BK through splice S168 to ground G100.

When does the MIL indicator light up?

The indicator lights with the ignition switch in the ON position 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 heated oxygen sensor do according to this diagram?

It provides a voltage related to oxygen content of exhaust gases to the PCM for regulating air/fuel ratio.

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1995 Ford Bronco 5.8L California Wiring Diagram 25-11 – MIL & Heated O2 Sensor

Engine controls 5.8L California wiring diagram with PCM, oxygen sensor, MIL and color-coded circuits

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Wiring diagram for 5.8L California engine controls showing the powertrain control module, heated oxygen sensor, malfunction indicator lamp and color-coded circuits.

AI caption December 2011 · Photo 1006 of 1799

This document is page 25-11 of a Ford factory wiring diagram set covering Engine Controls for the 5.8L (California emissions) engine. It shows the circuits for the Malfunction Indicator Lamp (MIL) in the instrument cluster and the LH Heated Oxygen Sensor (HO2S), and how they connect to the Powertrain Control Module (PCM). The MIL circuit is powered through fuse 17 (10A, 'Hot in Start or Run') in the fuse panel via circuit 640 R/Y, through connectors C250/C251, then circuit 658 PK/LG through C202 and the Data Link Connector (DLC) to PCM pin 17. The heated oxygen sensor heater is powered through fuse E (15A, 'Hot in Run') in the engine compartment fuse box via circuit 298 P/O; the sensor signal travels on circuit 94 R/BK through C110 to PCM pin 43, with sensor ground on circuit 57 BK through splice S168 to ground G100. A GY/R circuit 359 from C103 (page 25-10) branches via splice S146 (GN/R) to the E4OD transmission (page 30-1). PCM pin 10 connects to the A/C-heater system (198 DG/O) and pin 29 uses circuit 766 BK/LG. Notes explain MIL operation and the HO2S function.

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Frequently asked questions

Which fuse powers the Malfunction Indicator Lamp (MIL) circuit?: Fuse 17, a 10A fuse in the fuse panel (pages 13-3), hot in Start or Run, feeding circuit 640 R/Y.
Which fuse powers the LH heated oxygen sensor?: Fuse E, a 15A fuse in the engine compartment fuse box (pages 13-4), hot in Run, on circuit 298 P/O.
What wire color and PCM pin does the LH HO2S signal use?: The signal is on circuit 94 R/BK, passing through connectors C110F/C110M to PCM pin 43; the sensor ground is 57 BK through splice S168 to ground G100.
When does the MIL indicator light up?: The indicator lights with the ignition switch in the ON position 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 heated oxygen sensor do according to this diagram?: It provides a voltage related to oxygen content of exhaust gases to the PCM for regulating air/fuel ratio.