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.

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Engine Oil Pressure Sensor Signal Circuit | 1 | P0520 | P0520 | --
Engine Oil Pressure Sensor Ground Circuit | -- | P0520 | -- | --
1. Engine Oil Pressure Indicator Malfunction

### Circuit/System Description

The engine oil pressure (EOP) switch is a normally closed switch that opens with the proper oil pressure. With the ignition switch turned ON and the engine not running, the engine control module (ECM) should detect a low signal voltage input. With the engine running, the pressure switch opens, and the ECM should detect a high signal voltage input. When the oil pressure is low, the ECM sends a serial data message to the IPC requesting the EOP indicator turned ON.

### Reference Information

#### Schematic Reference

Instrument Cluster Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Instrument Cluster Description and Operation

#### 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

Ignition ON, engine running, verify the scan tool Oil Pressure parameter is Normal.

⇒ | If not the specified value, refer to Oil Pressure Diagnosis and Testing

### Circuit/System Testing

Important: Do not turn the key to the crank position or engage the starter at any time during diagnosis.

1. Ignition OFF, disconnect the harness connector at the engine oil pressure (EOP) switch.
2. Ignition ON, verify the scan tool Oil Pressure parameter is Normal.

⇒ | If not the specified value, test the signal circuit terminal 1 for a short to ground. If the circuit tests normal, replace the ECM.

3. Ignition ON, install a 3-Amp fused jumper wire between the signal circuit terminal 1 and ground. Verify the scan tool Oil Pressure parameter is Low Pressure.

⇒ | If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

4. If all circuits test normal, replace the engine oil pressure switch.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Engine Oil Pressure Sensor and/or Switch Replacement

• | Control Module References for the ECM replacement, setup, and programming