Malfunction Indicator Lamp: Testing and Inspection

Malfunction Indicator Lamp (MIL) Diagnosis

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.

* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Circuit/System Description

The malfunction indicator lamp (MIL) illuminates to inform the driver that an emission system fault has occurred and the engine control system requires service. Ignition voltage is supplied directly to the MIL and, when the emission fault occurs, the engine control module (ECM) turn the MIL ON by grounding the MIL control circuit. Under normal operating conditions, the MIL should be ON only when the ignition is ON and the engine is OFF.

Reference Information

Schematic Reference

* Engine Controls Schematics [1][2]Electrical Diagrams

* Instrument Cluster Schematics Instrument Cluster Schematics

Connector End View Reference

Component Connector End Views Fuel Pump and Level Sensor Assembly

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References Control Module References

Circuit/System Verification

Note: Any MIL requesting DTCs that may be set should be diagnosed first.

1. Ignition ON.

2. Verify that the P16 Instrument Cluster warning indicators are all illuminated.

• If the warning indicators do not illuminate
Refer to Symptoms - Displays and Gauges Symptoms - Displays and Gauges

• If the warning indicators illuminate

3. Verify all the scan tool parameters listed below display OK or Not Run when commanding the MIL ON and OFF with a scan tool.

* The MIL Control Circuit Low Voltage Test Status

* The MIL Control Circuit Open test Status

* The MIL Control Circuit High Voltage test Status

• If Malfunction displayed
Refer to Circuit/System Testing.

• If OK or Not Run displayed

4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

• If the DTC sets
Refer to Circuit/System Testing

• If the DTC does not set

5. All OK.

Circuit/System Testing

1. Ignition ON.

2. Ignition OFF, disconnect the harness connector at the P16 Instrument Cluster.

3. Connect a test lamp between the control circuit terminal 25 and B+ circuit terminal.

4. Verify the test lamp turns ON and OFF when commanding the ECM Malfunction Indicator Lamp (MIL) ON and OFF with a scan tool.

• If the test lamp is always OFF

1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module, ignition ON.

2. Test for less than 1 V between the control circuit and ground.

• If 1 V or greater, repair the short to voltage on the circuit.

• If less than 1 V

3. Ignition OFF.

4. Test for less than 2 ohms in the control circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, replace the K20 Engine Control Module.

• If the test lamp is always ON

1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.

2. Test for infinite resistance between the control circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance, replace the K20 Engine Control Module.

• If the test lamp turns ON and OFF

5. Test or replace the P16 Instrument Cluster.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the repair.

* Instrument Cluster Replacement Service and Repair

* Control Module References Control Module References for ECM replacement, programming, and setup.