Schematic Reference: Engine Controls Schematics
Circuit Description
There should be a steady MIL when the ignition is ON, prior to starting the engine. Battery ignition voltage is supplied to the MIL. The engine control module (ECM) will turn the MIL ON by grounding the control circuit at the ECM. A steady MIL with the engine running suggests a short to ground in the MIL control circuit or a stored DTC.
Diagnostic Aids
Check for a shorted to ground MIL control circuit between the ECM, I/P Cluster Assembly, and the duty check data link connector.
A shorted I/P Cluster Assembly board may cause the MIL to stay ON.
An intermittent malfunction may be caused by a fault in an MIL control system electrical circuit. Inspect the wiring harness and components for any of the following conditions:
| • | Backed out terminals. |
| • | Improper mating of terminals. |
| • | Broken electrical connector locks. |
| • | Improperly formed or damaged terminals. |
| • | Faulty terminal to wire connections. |
| • | Physical damage to the wiring harness. |
| • | A broken wire inside the insulation. |
| • | Corrosion of electrical connections, splices, or terminals. |
Test Description
The numbers below refer to the step numbers in the Diagnostic Table.
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The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
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Check for a short to ground in MIL control circuit.
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Check for a short in the MIL control circuit between the ECM and the duty check data link connector and the I/P cluster assembly, a short on this wire will turn the MIL ON.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||
Is the MIL illuminated? | -- | |||
Check for a short to ground in the MIL control circuit between the ECM and the I/P Cluster Assembly. Repair as necessary. Was a repair necessary? | -- | |||
4 | Check the I/P Cluster Assembly for a shorted circuit board. Repair or replace as necessary. Is the action complete? | -- | -- | |
5 | Replace the ECM. Refer to Engine Control Module Replacement. Is the action complete? | -- | -- | |
6 | After the repairs are completed start the engine and observe the MIL. Did the MIL illuminate for approximately 3 seconds and then turn OFF? | -- | System OK | Go to Applicable Diagnostic Table |
