For 1990-2009 cars

### 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 an intermittent condition. Refer to Intermittent Conditions .

### Test Description

The numbers below refer to the step numbers in the diagnostic table.

1. The Diagnostic System Check-Engine Controls 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.

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: Engine Controls Schematics
1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls
2 |

1. Turn OFF the ignition.
2. Disconnect the PCM.
3. Turn ON the ignition, leaving the engine OFF.

Is the malfunction indicator lamp (MIL) illuminated?

Go to Step 3

Go to Step 5

3 |

1. Check for a short to ground in the MIL control circuit between the PCM and the instrument panel cluster (IPC) assembly.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

Go to Step 6

Go to Step 4

4 |

1. Check the IPC assembly for a shorted circuit board.
2. Repair or replace as necessary. Refer to Printed Instrument Cluster Circuit Replacement in Instrument Panel, Gauges, and Console.

Is the action complete?

Go to Step 6

--

5 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | Go to Step 6 | --
6 | Start the engine and observe the MIL. Does the MIL turn OFF in approximately 1 to 2 seconds after the engine is started? | System OK | Go to Diagnostic System Check - Engine Controls