Pinpoint Test Z : The Mil (Malfunction Indicator Lamp) Is Never Or Always On

Normal Operation and Fault Conditions
If the engine MIL request 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 engine MIL request message is missing for 5 seconds or longer from the PCM, the BCM sets DTC U0100:00.

If the engine MIL request message is missing for 5 seconds or longer from the BCM, the IPC sets DTC U0100:00 and defaults the MIL on.

See MIL. REFER to: Instrument Panel Cluster (IPC) - System Operation and Component Description .

Possible Sources
- PCM concern
- IPC

Z1 RETRIEVE THE RECORDED DIAGNOSTIC TROUBLE CODES (DTCS) FROM THE IPC (INSTRUMENT PANEL CLUSTER) SELF-TEST
- Ignition ON.
- Using a diagnostic scan tool, perform the IPC self-test.
Are any DTC recorded?

Yes REFER to DTC Chart: IPC .

No GO to Z2

Z2 RETRIEVE THE RECORDED DIAGNOSTIC TROUBLE CODES (DTCS) FROM THE BCM (BODY CONTROL MODULE) SELF-TEST
- Using a diagnostic scan tool, perform the BCM self-test.
Are any Diagnostic Trouble Codes (DTCs) recorded?

Yes REFER to: Body Control Module (BCM) .

No GO to Z3

Z3 CARRY OUT THE IPC (INSTRUMENT PANEL CLUSTER) INDICATOR LAMP CONTROL ACTIVE COMMAND USING A DIAGNOSTIC SCAN TOOL

Using a diagnostic scan tool, view the IPC Parameter Identifications (PIDs).

Select the IPC MIL (MIL) PID.

Command the MIL on and off while observing the indicator.

Does the MIL illuminate when commanded on and turn off when commanded off?

Yes	If the MIL is never on, the system is operating correctly. If the MIL is always on, DIAGNOSE any PCM Diagnostic Trouble Codes (DTCs). Refer to Engine Controls - Powertrain DTC Charts & Descriptions (Except Diesel & Hybrid) or Engine Controls - Powertrain DTC Charts & Descriptions (Diesel) .

No	Refer to IPC Guided Routine Testing .