Pinpoint Test X: The Malfunction Indicator Lamp (MIL) Is Never/Always On

Instrumentation, Message Center and Warning Chimes

Pinpoint Tests

Pinpoint Test X: The Malfunction Indicator Lamp (MIL) Is Never/Always On

Normal Operation

The Malfunction Indicator Lamp (MIL) is controlled by the Instrument Panel Cluster (IPC) using data sent from the PCM over the High Speed Controller Area Network (HS-CAN) communication bus.

If the MIL status message is missing or invalid for less than 5 seconds, the IPC defaults the MIL to its last state (on or off) based upon the last known good message received. If the MIL status message is missing for more than 5 seconds, the IPC sets DTC U0100:00 in continuous memory and defaults the MIL on.

NOTE: If DTC U0100:00 sets in the IPC, other observable symptoms may be an inoperative speedometer, tachometer or odometer.

This pinpoint test is intended to diagnose the following:

- PCM
- IPC

PINPOINT TEST X: THE MIL IS NEVER/ALWAYS ON

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X1 CARRY OUT THE IPC MIL ACTIVE COMMAND USING THE SCAN TOOL

- Ignition ON.
- Enter the following diagnostic mode on the scan tool: IPC DataLogger.
- Select the IPC MIL (MIL) active command. Command the MIL on and off. Observe the MIL.
- Does the MIL illuminate when selected on and turn off when selected off?

Yes
GO to X2.

No
INSTALL a new IPC. REFER to Instrument Panel Cluster (IPC) Instrument Panel Cluster (IPC). TEST the system for normal operation.

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X2 RETRIEVE THE RECORDED DTCs FROM THE PCM KOEO SELF-TEST

- Check the recorded PCM DTCs from the KOEO self-test.
- Are any PCM DTCs recorded?

Yes
REFER to Computers and Control Systems. TEST the system for normal operation.

No
GO to X3.

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X3 RETRIEVE THE RECORDED DTCs FROM THE IPC SELF-TEST

- Check for recorded IPC DTCs from the self-test.
- Is DTC U0100:00 recorded?

Yes
GO to Pinpoint Test BA. Pinpoint Tests BA: DTC U0100:00

No
If the MIL is never on, the system is operating correctly at this time. If the MIL is always on, INSTALL a new PCM. REFER to Electronic Engine Controls Service and Repair. TEST the system for normal operation.

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