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
--- | --- | --- | --- | ---
Oil Pressure Switch Signal | 1 | P0520 | 1 | --
Low Reference | -- | P0520 | -- | --
1. Engine Oil Pressure Indicator Malfunction

### Circuit 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 body control module (BCM) requesting the EOP indicator turned ON. The instrument panel cluster (IPC) illuminates the EOP indicator when the IPC receives a serial data message from the BCM requesting the EOP indicator turned ON.

### Reference Information

#### Schematic Reference

Instrument Cluster Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

• | Indicator/Warning Message 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 Engine Oil Pressure Switch parameter is OK.

⇒ | If not the specified value, refer to:

• | Oil Pressure Diagnosis and Testing for the 2.9L engine

• | Oil Pressure Diagnosis and Testing for the 3.7L engine

• | Oil Pressure Diagnosis and Testing for the 4.8L, 5.3L, 6.0L, 6.2L or 7.0L engine

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the engine oil pressure (EOP) switch.
2. Ignition OFF, test for less than 1 ohm between the low reference circuit terminal B and ground.

⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

3. Ignition ON, verify the scan tool Engine Oil Pressure Switch parameter is OK.

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

4. Ignition ON, install a 3A fused jumper wire between the signal circuit terminal A and the ground circuit terminal B. Verify the scan tool Engine Oil Pressure Switch parameter is Low.

⇒ | If not the specified value, test the signal circuit for an open/high resistance. If circuit test normal, replace the ECM.

⇒ | Ignition ON, command the indicators OFF with the scan tool.

⇒ | If the EOP indicator does not turn OFF, replace the IPC.

5. If all circuits test normal, test or 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 for the 2.9L engine

• | Engine Oil Pressure Sensor and/or Switch Replacement for the 3.7L engine

• | Engine Oil Pressure Sensor and/or Switch Replacement for the 4.8L, 5.3L, 6.0L, 6.2L or 7.0L engine

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