Refer to Engine Controls Schematics
Power and Ground
and
MIL and DLC
.
Circuit Description
There should be a steady malfunction indicator lamp (MIL) when the ignition is ON, prior to starting the engine. Battery ignition voltage is supplied to the MIL. The powertrain control module (PCM) will turn the MIL ON by grounding the control circuit at the PCM. A steady MIL with the engine running suggests a short to ground in the MIL control circuit, or a DTC is stored.
Diagnostic Aids
An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside the insulation. Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before any component replacement.
| • | Check for a shorted MIL control circuit between the PCM and the instrument panel cluster (IPC) assembly. |
| • | A shorted IPC assembly board may cause the MIL to stay on. |
Test Description
The numbers below refer to the step numbers in the diagnostic table.
-
The 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.
-
Disconnecting the PCM will determine whether the malfunction is caused by a short to ground in the MIL control circuit or a faulty PCM.
Step | Action | Value | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||
Is the MIL ON? | -- | |||
3 |
Is the action complete? | -- | -- | |
4 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | -- | |
5 | Start the engine and observe the MIL. Does the MIL turn OFF approximately 1 to 2 seconds after the engine is started? | -- | System OK |
