Malfunction Indicator Lamp (MIL) Always On

Diagnostic Chart:

Refer to Engine Controls Power And Ground Schematics and to Engine Controls MIL and DLC Schematics.

CIRCUIT DESCRIPTION
The Malfunction Indicator Lamp (MIL) is illuminated when the ignition is on and the engine is off. 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. The MIL is normally 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 Instrument Panel Cluster (IPC) assembly.
^ A shorted IPC assembly board may cause the MIL to remain illuminated.
^ Check for a faulty electrical connection to the PCM.

An intermittent malfunction may be caused by a fault in the MIL electrical circuit. Inspect the wiring harness and components for any of the following conditions:
^ Any backed-out terminals
^ Any improper mating of terminals
^ Any broken electrical connector locks
^ Any improperly formed or damaged terminals
^ Any faulty terminal-to-wire connections
^ Any physical damage to the wiring harness
^ A broken wire inside the insulation
^ Any corrosion of electrical connections, the splices, or the 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 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.
2. This step checks for a short to ground in MIL control circuit.
3. This step checks for a short in the MIL control circuit between the PCM and the Instrument Panel Cluster (IPC) assembly.