GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2008 🢒 Lucerne 🢒 Engine 🢒 Engine Controls and Fuel - 3.8L 🢒 Malfunction Indicator Lamp (MIL) Diagnosis

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Circuit/System Description

The malfunction indicator lamp (MIL) is located on the instrument panel cluster (IPC).

The MIL informs the driver that an emission system fault has occurred and that the engine control system requires service. The powertrain control module (PCM) monitors the MIL control circuit for conditions that are incorrect for the commanded states of the MIL. For example, a failure condition exists if the PCM detects low voltage when the MIL is commanded OFF, or high voltage when the MIL is commanded ON.

Reference Information

Schematic Reference

    •  Engine Controls Schematics
    •  Instrument Cluster Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification
  1. Ignition ON, command the MIL ON and OFF with a scan tool. The MIL should turn ON and OFF as commanded.
  2. Command the MIL ON and OFF with a scan tool while observing the MIL Circuit Status parameter.
    3. ⇒The parameter should indicate OK.
  3. Operate the vehicle within the Conditions for Running the DTC to verify that the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing
  1. Ignition ON, verify that the (IPC) warning indicators are illuminated.
    2. ⇒If the IPC warning indicators are not illuminated, test the IPC ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, replace the IPC.
  2. Ignition OFF, disconnect the PCM X1 harness connector. Ignition ON, the MIL should not illuminate.
    3. ⇒If the MIL is illuminated, test the MIL control circuit terminal 6 for a short to ground. If the circuit tests normal, replace the IPC.
  3. Ignition ON, connect a 3A fused jumper wire between the MIL control circuit terminal 6 and ground. The MIL should illuminate.
    4. ⇒If the MIL does not illuminate, test the MIL control circuit for a short to voltage, or an open/high resistance. If the circuit tests normal, replace the IPC/bulb.
  4. If all circuits/connections test normal, replace the PCM. Ignition ON, verify that the IPC warning indicators are illuminated.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Instrument Cluster Replacement
    •  Control Module References for PCM replacement, setup and programming