P0521-ENGINE OIL PRESSURE SENSOR PERFORMANCE

For a complete wiring diagram Refer to Section 8W.

When Monitored:
Engine running.
Set Condition:
The engine oil pressure never reaches the calibrated specification with the engine RPM at 1250. One trip fault.

Possible Causes

ENGINE OIL/ENGINE MECHANICAL

EXCESSIVE RESISTANCE IN THE (G6) ENGINE OIL PRESSURE SENSOR SIGNAL CIRCUIT

EXCESSIVE RESISTANCE IN THE (F855) 5-VOLT SUPPLY CIRCUIT

EXCESSIVE RESISTANCE IN THE (K900) SENSOR RETURN CIRCUIT

ENGINE OIL PRESSURE SENSOR

PCM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).

Diagnostic Test

1. ACTIVE DTC

NOTE: Make sure that the engine oil is at the proper level. Also, check the customers oil change history to ensure that the oil is being changed at the correct intervals and that the proper oil viscosity is being used.

Ignition on, engine not running.
With a scan tool, select View DTCs.

Is the DTC Active at this time?

Yes

Go To 2

Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

2. ENGINE OIL/ENGINE MECHANICAL

NOTE: The following items must be considered before determining the cause of this DTC. Failure to do so may lead to misdiagnosis.

ENGINE MECHANICAL TOLERANCES OUT OF SPECIFICATION
ENGINE OIL PRESSURE OUT OF SPECIFICATION
LOW ENGINE OIL
OIL DIRTY OR DETERIORATED (Lack of scheduled oil changes)
ENGINE OIL CONTAMINATED (i.e., coolant and/or fuel)

If any of the above conditions are found, repair as necessary.

Were any of the above conditions present?

Yes

Repair as necessary.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go To 3

3. ENGINE OIL PRESSURE SENSOR

Turn the ignition off.
Disconnect the Engine Oil Pressure Sensor connector.
Ignition on, engine not running.
With a scan tool, monitor the Engine Oil Pressure Sensor voltage.
Connect a jumper wire between the (K900) Sensor Ground circuit and the (G6) Engine Oil Pressure Signal circuit.

NOTE: Engine Oil Pressure voltage should change from approximately 4.5 volts to less than 0.5 of a volt.

Is the voltage reading within the listed specification when the jumper wire is installed?

Yes

Remove the Engine Oil Pressure sensor and ensure the oil passage/port is free from any blockage. If OK, replace the Engine Oil Pressure Sensor.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go To 4
NOTE: Remove the jumper wire before continuing.

4. EXCESSIVE RESISTANCE IN THE (G6) ENGINE OIL PRESSURE SIGNAL CIRCUIT

Turn the ignition off.
Connect the Engine Oil Pressure Sensor connector.
Disconnect the C1 PCM harness connector.

CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 along with the #8815-1 to perform the diagnosis.

Using a voltmeter perform a voltage drop test. Backprobe the (G6) Engine Oil Pressure Signal circuit at the Throttle Body harness connector and probe the appropriate terminal of the special tool #8815. Make sure the voltmeter leads are connected so a positive polarity is displayed on the voltmeter.

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.

Start the engine and allow it to reach normal operating temperature.
Monitor the voltmeter.

Is the voltage below 0.5 of a volt?

Yes

Go To 5

Repair the excessive resistance in the (G6) Engine Oil Pressure Signal circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

5. EXCESSIVE RESISTANCE IN THE (F855) 5-VOLT SUPPLY CIRCUIT

Turn the Ignition off.
Remove special tool #8815 from the C1 PCM harness connector and Re-Connect the C1 PCM harness connector to the PCM.
Disconnect the C2 PCM harness connector to install special tool #8815 and #8815-1.
Using a voltmeter perform a voltage drop test. Backprobe the (F855) 5-volt Supply circuit at the Throttle Body harness connector and probe the appropriate terminal of the special tool #8815. Make sure the voltmeter leads are connected so a positive polarity is displayed on the voltmeter.

Start the engine and allow it to reach normal operating temperature.
Monitor the voltmeter.

Is the voltage below 0.5 of a volt?

Yes

Go To 6

Repair the excessive resistance in the (F855) 5-volt Supply circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

6. EXCESSIVE RESISTANCE IN THE (K900) SENSOR GROUND CIRCUIT

Turn the Ignition off.
Move your volt meter leads to backprobe the (K900) Sensor Ground circuit at the Throttle Body harness connector and to probe the appropriate terminal of the special tool #8815. Make sure the voltmeter leads are connected so a positive polarity is displayed on the voltmeter.

Start the engine and allow it to reach normal operating temperature.
Monitor the voltmeter.

Is the voltage below 0.5 of a volt?

Yes

Go To 7

Repair the excessive resistance in the (K900) Sensor Ground circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

7. PCM

NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.

Were there any problems found?

Yes

Repair as necessary.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Replace and program the Powertrain Control Module per Service Information.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)