For 1990-2009 cars

### 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 diagnostic trouble code (DTC) is stored.

### Diagnostic Aids

Check for the following conditions:

• | 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.

An intermittent malfunction may be caused by a faulty electrical connection. Refer to Intermittent Conditions .

### Test Description

The numbers below refer to the step numbers on 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. 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 | 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 electrical connector with the MIL control circuit.
3. Turn ON the ignition, with the engine OFF.

Is the MIL ON?

Go to Step 3

Go to Step 4

3 |

1. Repair the short to ground in the MIL control circuit between the PCM and the IPC assembly.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

Go to Step 5

--

4 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | Go to Step 5 | --
5 | Start the engine and observe the MIL. Does the MIL turn OFF approximately 1 to 2 seconds after the engine is started? | Go to Step 6 | Go to Step 2
6 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | Go to Diagnostic Trouble Code (DTC) List | System OK