P051C

P051C-CRANKCASE PRESSURE SENSOR CIRCUIT LOW







Theory of Operation

The Crankcase Pressure Sensor is used to monitor the pressure inside the crankcase. The Engine Control Module (ECM) supplies the Crankcase Pressure Sensor a 5-Volt reference voltage. When the crankcase pressure is low, the sensor signal voltage is low. When the crankcase pressure is high, the sensor signal voltage is near the 5-Volt reference voltage. The ECM monitors the Crankcase Pressure Sensor Signal circuit voltage to calculate the pressure of the air within the crankcase. The ECM does not illuminate the MIL or ETC lamp for any of the crankcase pressure faults.

- When Monitored:
Ignition on, engine not running.

- Set Condition:
The circuit voltage to the Engine Control Module (ECM) is below a calibrated threshold for a calibrated time.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. OTHER DTCS
1. Ignition on, engine not running.
2. With the scan tool, read DTCs.

Are there any 5-Volt Reference DTCs present?

Yes

- Repair the 5-Volt Reference DTCs before proceeding.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 2

2. P051C ACTIVE

Is DTC P051C active?

Yes

- Go To 3

No

- Perform the INTERMITTENT CONDITION - 6.7L diagnostic procedure. Intermittent Condition Test.

3. CHECK THE (F855) 5-VOLT SUPPLY CIRCUIT




1. Turn the ignition off.
2. Disconnect the Crankcase Pressure Sensor harness connector.

NOTE: Check connectors - Clean/repair as necessary.

3. Turn the ignition on.
4. Measure the voltage across the (F855) 5-Volt Supply circuit and the (K916) Sensor Return circuit at the Crankcase Pressure Sensor harness connector.

Is the voltage between 4.9 and 5.1 Volts?

Yes

- Go To 4

No

- Repair the (F855) 5-Volt Supply circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

4. CHECK THE CRANKCASE PRESSURE SENSOR




1. While monitoring scan tool, connect a jumper between the (F855) 5-Volt Supply circuit and the (K926) Crankcase Pressure Sensor Signal circuit at the Crankcase Pressure Sensor harness connector.

Does the scan tool display DTC P051D as active and P051C as stored with the jumper in place?

Yes

- Replace the Crankcase Pressure Sensor.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 5

5. CHECK FOR THE (K926) CRANKCASE PRESSURE SENSOR SIGNAL CIRCUIT SHORTED TO THE (K916) SENSOR GROUND CIRCUIT




1. Turn the ignition off.
2. Remove the jumper.
3. Disconnect the ECM C1 harness connector.

NOTE: Check connectors - Clean/repair as necessary.

4. Measure the resistance between the (K926) Crankcase Pressure Sensor Signal circuit and (K916) Sensor Ground circuit in the Crankcase Pressure Sensor harness connector.

Is the resistance above 10k Ohms?

Yes

- Go To 6

No

- Repair the short between the (K926) Crankcase Pressure Sensor Signal circuit and (K916) Sensor Ground circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

6. CHECK THE (K926) CRANKCASE PRESSURE SIGNAL CIRCUIT FOR A SHORT TO GROUND




1. Measure the resistance between ground and the (K926) Crankcase Pressure Sensor Signal circuit at the Crankcase Pressure Sensor harness connector.

Is the resistance above 10k Ohms?

Yes

- Go To 7

No

- Repair the (K926) Crankcase Pressure Sensor Signal circuit for a short to ground.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

7. CHECK THE (K926) CRANKCASE PRESSURE SENSOR SIGNAL CIRCUIT FOR AN OPEN




1. Measure the resistance of the (K926) Crankcase Pressure Signal circuit between the Crankcase Pressure Sensor harness connector and the ECM C1 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Replace the Engine Control Module (ECM).
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Repair the (K926) Crankcase Pressure Signal circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.