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 P0521: Engine Oil Pressure (EOP) Sensor Performance
DTC P0522: Engine Oil Pressure (EOP) Sensor Circuit Low Voltage
DTC P0523: Engine Oil Pressure (EOP) Sensor Circuit High Voltage

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
5-Volt Reference | P0522 | P0523 | P0523 | P0521
Signal | P0522 | P0523 | P0523 | P0521
Low Reference | -- | P0523 | -- | P0521

### Circuit/System Description

The engine oil pressure sensor changes voltage based on the engine oil pressure. The engine oil pressure sensor is a 3-wire sensor comprised of the signal circuit, the low reference circuit and the 5-volt reference circuit. The engine control module (ECM) supplies 5 V to the engine oil pressure sensor via the 5-volt reference circuit and provides ground via the engine oil pressure sensor low reference circuit. The ECM monitors the signal circuit of the engine oil pressure sensor to determine the engine oil pressure sensor voltage is within the normal operating range of approximately 1-4 V. When the engine oil pressure is high, the engine oil pressure sensor voltage is high and the sensor senses a high signal voltage. When the engine oil pressure is low, the engine oil pressure sensor voltage is low and the ECM senses a low signal voltage. The ECM sends the engine oil pressure sensor information via High Speed CAN-Bus to the body control module (BCM). The BCM then sends the engine oil pressure sensor information via Low Speed CAN-Bus to the instrument cluster.

### Conditions for Running the DTC

The engine is running

### Conditions for Setting the DTC

#### P0521

• | The engine oil pressure is out of its working range.

• | The ECM does not detect a change in the engine oil pressure.

• | The above condition is present over a predetermined variance of engine speed.

#### P0522

• | The ECM detects a short to ground in the engine oil pressure signal circuit.

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

#### P0523

• | The ECM detects a short to voltage or an open circuit in the engine oil pressure signal circuit.

• | 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.

### 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

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

Engine running, observe the scan tool Engine Oil Pressure Sensor parameter. The reading should be between 0.3-4.8 V.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the B37 Engine Oil Pressure (EOP) Switch.
2. Ignition OFF, test for less than 5 Ω between the low reference circuit terminal 1 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 K20 Engine Control Module (ECM).

3. Ignition ON, test for 4.8-5.2 V between the 5-volt reference circuit terminal 2 and ground.

⇒ | If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

⇒ | If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

4. Verify the scan tool Engine Oil Pressure Sensor is greater than 4.8 V.

⇒ | If less than the specified range, test the signal circuit terminal 3 for a short to ground. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

5. Install a 3 A fused jumper wire between the signal circuit terminal 3 and the low reference circuit terminal 1. Verify the scan tool Engine Oil Pressure Sensor is less than 0.3 V.

⇒ | If greater than the specified range, 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).

6. If all circuits test normal, replace the B37 Engine Oil Pressure (EOP) Switch.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Engine Oil Pressure Sensor Replacement for LBW.

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