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

Instrumentation and Warning Chimes

Pinpoint Tests

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

Normal Operation

The Malfunction Indicator Lamp (MIL) is controlled by the Instrument Cluster (IC) 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 MIL remains in the last indication mode (on or off), based upon the last known good data message. If the MIL status message is missing for more than 5 seconds, the IC sets DTC U0100 in continuous memory and defaults the MIL on. If the MIL message is deemed invalid for longer than 5 seconds, the IC defaults the MIL on.

NOTE: If DTC U0100 is set in the IC, other observable symptoms may be an inoperative speedometer, tachometer or odometer.

This pinpoint test is intended to diagnose the following:

- PCM
- IC


PINPOINT TEST Q: THE MIL IS NEVER/ALWAYS ON

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Q1 CARRY OUT THE IC WARNING LAMPS AND CHIME ACTIVE COMMAND USING THE SCAN TOOL


- Ignition ON.
- Enter the following diagnostic mode on the scan tool: IC DataLogger.
- Select the IC MIL (MIL_IC) 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 Q2.

No
INSTALL a new IC. REFER to Instrument Cluster (IC) Service and Repair. TEST the system for normal operation.

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Q2 RETRIEVE THE RECORDED DTCs FROM THE KOEO PCM SELF-TEST


- Check the recorded PCM DTCs from the Key ON Engine OFF (KOEO) self-test.
- Are any DTCs recorded?

Yes
REFER to Computers and Control Systems.

No
GO to Q3.

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Q3 RETRIEVE THE RECORDED DTCs FROM THE IC SELF-TEST


- Check for recorded IC DTCs from the self-test.
- Are any DTCs recorded?

Yes
For DTC U0100, GO to Pinpoint Test AJ. Pinpoint Test AJ: DTC U0100

For all other DTCs, REFER to DTC Charts. Diagnostic Trouble Code Tests and Associated Procedures

No
If the MIL is always on, INSTALL a new PCM. REFER to Electronic Engine Controls Service and Repair. TEST the system for normal operation.

If the MIL is never on, the system is functioning correctly.

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