P0521

DTC P0521

DTC Descriptor

DTC P0521
- Engine Oil Pressure (EOP) Sensor Performance

Diagnostic Fault Information

Important: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview






Circuit/System Description

The engine oil pressure (EOP) sensor changes resistance based on the engine oil pressure. The EOP sensor is a 3-wire sensor comprising of the signal circuit, the low reference circuit and the 5-volt reference circuit. The engine control module (ECM) supplies 5-volts to the EOP sensor via the 5-volt reference circuit and provides ground via the EOP low reference circuit. The ECM monitors the signal circuit of the EOP sensor to determine if the engine oil pressure sensor voltage is within the normal operating range of approximately 1-4 volts. When the engine oil pressure is high, the EOP sensor resistance is high and the ECM senses a high signal voltage. When the engine oil pressure is low, the EOP sensor resistance is low and the ECM senses a low signal voltage. The ECM sends the EOP information to the instrument panel cluster (IPC) via GMLAN serial data message. The ECM can also predict oil pressure as a function of engine speed and engine temperature.

Conditions for Running the DTC

* The engine is running with engine speed between 1000 and 3500 RPM.
* Oil temperature is less than 140 C (284 F).

Conditions for Setting the DTC

The ECM does not detect a change in the engine oil pressure of at least 34.5 kPa (5 psi) over a predetermined variance of the engine speed.

Action Taken When the DTC Sets

* The ECM records the operating conditions at the time the diagnostics test fails. The ECM displays this information in the Failure Records on the scan tool.
* The instrument panel cluster (IPC) illuminates the EOP indicator.

Conditions for Clearing the DTC

* The DTC becomes history when the conditions for setting the DTC are no longer present.
* The history DTC clears after 40 malfunction-free warm-up cycles.
* The ECM receives a clear code command from the scan tool.

Circuit/System Verification

Engine ON, observe the Engine Oil Pressure Sensor parameter. The reading should be between 41 kPa (6 psi) and 448 kPa (65 psi).

Circuit/System Testing

1. Engine ON, transmission in park and vary the engine speed by 500 RPM.
2. Verify the scan tool Engine Oil Pressure Sensor parameter changes by more than 34.5 kPa (5 psi).

• If less than 34.5 kPa (5 psi), replace the EOP sensor.

Repair Instructions

Important: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Engine Oil Pressure Sensor and/or Switch Replacement for the 6.0L engine
* Engine Oil Pressure Sensor and/or Switch Replacement for the 7.0L engine