For 1990-2009 cars

### 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.

### DTC Descriptor

DTC P0650: Malfunction Indicator Lamp (MIL) Control Circuit

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
MIL Voltage Supply | P0650 | P0650 | -- | --
MIL Control | P0650* | P0650 | P0650 | --
* The MIL remains ON

### 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 engine control module (ECM) monitors the MIL control circuit for conditions that are incorrect for the commanded state of the MIL. For example, a failure condition exists if the ECM detects low voltage when the MIL is commanded OFF, or high voltage when the MIL is commanded ON.

### Conditions for Running the DTC

• | The engine speed is greater than 80 RPM.

• | The ignition voltage is between 10-18 volts.

• | The ECM has commanded the MIL ON and OFF at least once during the ignition cycle.

• | DTC P0650 runs continuously once the above conditions are met.

### Conditions for Setting the DTC

• | The ECM detects an open, a short to ground, or a short to voltage on the circuit that controls the MIL.

• | The condition exists for at least 4 seconds.

### Action Taken When the DTC Sets

DTC P0650 is a Type B DTC.

### Conditions for Clearing the DTC

DTC P0650 is a Type B DTC.

### Diagnostic Aids

If the condition is intermittent, move the related harnesses and connectors with the engine operating. Observe the scan tool Circuit Test Status parameters for the component. The Circuit Test Status parameter will change from OK or Not Run to Fault if there is a condition with the circuit or a connection.

### Reference Information

#### Schematic Reference

Engine Controls 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

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. Ignition ON, observe the scan tool MIL circuit status parameters. Each of the MIL circuit status parameters should display OK or Not Run.
2. Ignition ON, command the MIL ON and OFF with a scan tool. The MIL should turn ON and OFF as commanded, and the MIL circuit status parameters should continue to display OK or Not Run in each commanded state.
3. Operate the vehicle within the Conditions for Running the DTC to verify 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. If any other IPC indicators or gages are inoperative, refer to Instrument Cluster Gages Inoperative.
2. Ignition OFF, disconnect the ECM harness connectors. Ignition ON, the MIL should not illuminate.

⇒ | If the MIL is illuminated, test the MIL control circuit terminal 54-X1 for a short to ground. If the circuit tests normal, replace the IPC.

3. Ignition ON, connect a 3 A fused jumper wire between the MIL control circuit terminal 54-X1 and ground. The MIL should illuminate.

⇒ | 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.

4. If all of the circuits/connections test normal, replace the ECM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Instrument Cluster Replacement

• | Control Module References for engine control module replacement, setup, and programming