Malfunction Indicator Lamp (MIL) Always On

Diagnostic Chart:

Engine Controls Schematics: Power And Ground:

Engine Controls Schematics: MIL And DLC:

CIRCUIT DESCRIPTION
The malfunction indicator lamp (MIL) illuminates when the ignition is ON, and the engine is OFF. Battery ignition voltage is supplied to the MIL. The PCM will turn the MIL ON by grounding the control circuit at the PCM. Under normal conditions, the MIL is OFF when the engine is running. A steady MIL with the engine running suggests a short to ground in the MIL control circuit, or a DTC is set in the powertrain control system.

DIAGNOSTIC AIDS
Check for any of the following conditions:
^ Check for a shorted MIL control circuit between the PCM and the instrument panel cluster assembly.
^ A shorted board in the instrument panel cluster assembly may cause the MIL to stay ON.
^ Check for a faulty electrical connection to the PCM.

A fault in the MIL electrical circuit may cause an intermittent malfunction. Inspect the wiring harness and the components for any of the following conditions:
^ Backed out terminals.
^ Incorrect mating of terminals.
^ Broken electrical connector locks.
^ Incorrectly formed terminals or damaged terminals.
^ Faulty terminal-to-wire connections.
^ Physical damage to the wiring harness.
^ A broken wire inside the insulation.
^ Corrosion of electrical connections, of splices, or of terminals.

TEST DESCRIPTION
The numbers below refer to the step numbers in the diagnostic table.
1. The Powertrain OBD System Check prompts the technician to complete some basic checks, and to save the applicable freeze frame data on the scan tool. This creates an electronic copy of the data that was taken when the fault occurred. The scan tool saves the information for later reference.
2. This step checks for a short to ground in the MIL control circuit.
3. This step checks for a short in the MIL control circuit between the PCM and the I/P cluster assembly.