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 P0520: Engine Oil Pressure (EOP) Switch Circuit Malfunction

### Diagnostic Fault Information

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

### Typical Scan Tool Data

#### ECM - Engine Oil Pressure Switch

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: Engine Running Parameter Normal Range: OK
Signal | Low | OK | OK
Ground | -- | OK | --

### Circuit/System Description

The engine oil pressure 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 engine oil pressure switch opens and the ECM should detect a high signal voltage input. When the oil pressure is low, the ECM sends a message via High Speed CAN-Bus to the body control module (BCM). The BCM then sends a message via Low Speed CAN-Bus to the instrument cluster requesting the engine oil pressure indicator turned ON.

### Conditions for Running the DTC

The engine is running

### Conditions for Setting the DTC

• | The ECM detects that the engine oil pressure switch signal circuit is pulled low.

• | The above condition is present for greater than 10 seconds.

### Action Taken When the DTC Sets

The instrument cluster illuminates the service vehicle soon indicator and the oil pressure low indicator.

### Conditions for Clearing the DTC

The DTC becomes history when the conditions for setting the DTC are no longer present.

### Reference Information

#### Schematic Reference

Instrument Cluster Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

• | Instrument Cluster Description and Operation

• | Indicator/Warning Message Description and Operation

• | Driver Information Center (DIC) 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, observe the scan tool Engine Oil Pressure Switch parameter with the ignition switch turned ON and the engine not running the reading should be Low, with the engine running the reading should be OK.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the B37 Engine Oil Pressure Switch.
2. Ignition ON, verify the scan tool Engine Oil Pressure Switch parameter is OK.

⇒ | If not the specified value, test the signal circuit terminal 1 for a short to ground. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

3. Install a 3 A fused jumper wire between the signal circuit terminal 1 and ground. Verify the scan tool Engine Oil Pressure Switch parameter is Low.

⇒ | 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 K20 Engine Control Module (ECM).

4. If all circuits test normal, test or replace the B37 Engine Oil Pressure Switch.

### Component Testing

#### Static Test

1. Ignition OFF, disconnect the harness connector at the B37 Engine Oil Pressure Switch.
2. Test for infinite resistance between the signal terminal 1 and ground with the switch in the open position.

⇒ | If not the specified value, replace the B37 Engine Oil Pressure Switch.

3. Test for less than 5 Ω between the signal terminal 1 and ground with the switch in the closed position.

⇒ | If greater than the specified range, replace the B37 Engine Oil Pressure Switch.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Link x Engine Oil Pressure Switch Replacement for LLW.

• | Link x Engine Oil Pressure Switch Replacement for LXV.

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