Malfunction Indicator Lamp (MIL) Always On

Malfunction Indicator Lamp (MIL) Always On

Circuit Description

The malfunction indicator lamp (MIL) is a light emitting diode (LED) that is controlled by a logic circuit and the powertrain control module (PCM). The PCM pulls the MIL control circuit low in order to illuminate the LED.


MIL Operation

The MIL and the logic circuit are located on the instrument panel cluster (IPC).

MIL Function

- The MIL informs the driver that a malfunction has occurred and the vehicle should be taken in for service as soon as possible.

- The MIL illuminates during a functional test of the MIL circuit and LED.

- A DTC will be stored if a MIL is requested by the diagnostic.

MIL Illumination

- The MIL will illuminate with ignition switch ON and the engine not running.

- The MIL will turn OFF when the engine is started.

- The MIL will remain ON if the self-diagnostic system has detected a malfunction.

- The MIL may turn OFF if the malfunction is not present.

- If the MIL is illuminated and then the engine stalls, the MIL will remain illuminated so long as the ignition switch is ON.

- It the MIL is not illuminated and the engine stalls, the MIL will not illuminate until the ignition switch is cycled OFF, then ON.


Diagnostic Aids

If the problem is intermittent, refer to Intermittent Conditions.Symptom Related Diagnostic Procedures


Test Description

Malfunction Indicator Lamp (MIL) Always On:

The number below refers to the step number on the diagnostic table.

2. This step determines if the condition is with the MIL control circuit or the IPC.