DTC P0521, P0522, or P0523. Cadillac STS 2008

For 1990-2009 cars only

Makes 🢒 Cadillac 🢒 2008 🢒 STS 🢒 DTC 🢒 DTC P0521, P0522, or P0523

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 Descriptors

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	High Resistance	Open	Short to Voltage	Signal Performance
Engine Oil Pressure 5-Volt Reference	P0522	1	P0522	P0523	P0521
Engine Oil Pressure Sensor Signal	P0522	1	P0522	P0523	P0521
Low Reference	--	1	P0523	--	P0521
1. Engine Oil Pressure Indicator Malfunction.

The engine oil pressure (EOP) sensor changes voltage 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 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 voltage is high and the ECM senses a high signal voltage. When the engine oil pressure is low, the EOP sensor voltage is low and the ECM senses a low signal voltage. The ECM sends the EOP information to the instrument panel cluster (IPC) via the serial data circuit.

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

P0521

•	The ECM does not detect a change in the engine oil pressure of at least 34.5 kPa (5.0 psi).

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

P0522

•	The ECM detects that the EOP sensor signal circuit is less than 0.2 volt.

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

P0523

•	The ECM detects that the EOP sensor signal circuit is greater than 4.8 volts.

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

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 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.

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, observe the scan tool Engine Oil Pressure Sensor parameter. The reading should be between 0.2-4.8 volts.
Verify the engine oil pressure, refer to:

•	Oil Pressure Diagnosis and Testing for the 3.6L engine

•	Oil Pressure Diagnosis and Testing for the 4.6L engine

•	Oil Pressure Diagnosis and Testing for the 4.4L engine

Circuit/System Testing

Ignition OFF, disconnect the harness connector at the engine oil pressure (EOP) sensor.
Ignition OFF, test for less than 1.0 ohm between the low reference circuit terminal listed below and ground.

•	Low reference circuit terminal A (LH2/LC3)

•	Low reference circuit terminal C

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

Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit listed below and ground.

•	5-volt reference circuit terminal A

•	5-volt reference circuit terminal C (LH2/LC3)

⇒	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 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 ECM.

Verify the scan tool Engine Oil Pressure Sensor parameter is less than 0.2 volt.

⇒	If greater than the specified range, test the signal circuit terminal B for a short to voltage. If the circuit tests normal, replace the ECM.

Install a 3A fused jumper wire between the signal circuit terminal B and the 5-volt reference circuit listed below. Verify the scan tool Engine Oil Pressure Sensor parameter is greater than 4.8 volts.

•	5-volt reference circuit terminal A

•	5-volt reference circuit terminal C (LH2/LC3)

⇒	If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

Ignition ON, with the scan tool command the engine oil pressure indicator OFF.

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

If all circuits test normal, test or replace the EOP sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

•	Engine Oil Pressure Sensor and/or Switch Replacement for 3.6L engine

•	Engine Oil Pressure Sensor and/or Switch Replacement for 4.6L engine

•	Engine Oil Pressure Sensor and/or Switch Replacement for 4.4L engine

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