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P051C






P051C-CRANKCASE PRESSURE SENSOR CIRCUIT LOW





For a complete wiring diagram, refer to the Wiring Information Electrical Diagrams. Electrical Diagrams

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 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:
At key on, engine not running the crankcase pressure sensor reading is higher than a calibrated threshold.





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 supply DTCs ?

Yes

- Repair other DTCs first.

No

- Go To 2

2. P051C ACTIVE

Is DTC P051C active?

Yes

- Go To 3

No

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

3. (F855) 5-VOLT SUPPLY CIRCUIT
1. Turn the ignition off.
2. Disconnect the Crankcase pressure sensor 1/1 harness connector.

NOTE: Check connectors - Clean/repair as necessary.

3. Turn the ignition on.
4. Measure the voltage between the (F855) 5-volt supply circuit to the (K916) Sensor Return circuit at the sensor harness connector.

Is the voltage between 4.5 and 5.5 volts?

Yes

- Go To 4

No

- Go To 6

4. CRANKCASE PRESSURE SENSOR
1. While monitoring scan tool, use a jumper wire to connect the (F855) 5-volt supply circuit with the (K926) Crankcase Pressure Signal circuit at the sensor harness connector.

Does the scan tool show a P051D DTC?

Yes

- Replace the Crankcase pressure sensor
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 5

5. (K926) CRANKCASE PRESSURE SIGNAL CIRCUIT SHORTED TO THE (K916) SENSOR GROUND CIRCUIT
1. Turn the ignition off.
2. Remove the jumper wire.
3. Disconnect the ECM harness connector.

NOTE: Check connectors - Clean/repair as necessary.

4. Turn the ignition on.
5. Measure the resistance between the (K926) Crankcase Pressure Signal circuit and (K916) Sensor ground circuit in the Crankcase pressure sensor harness connector.

Is the resistance greater than 10k Ohms?

Yes

- Go To 6

No

- Repair or replace the shorted wiring harness.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

6. (F855) 5-VOLT SUPPLY CIRCUIT SHORTED TO THE (K916) SENSOR GROUND
1. Turn the ignition off.
2. Measure the resistance between the (F855) 5-volt Supply circuit and (K916) Sensor ground circuit in the Crankcase pressure sensor harness connector.

Is the resistance greater than 10k Ohms?

Yes

- Go To 7

No

- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

7. (K926) CRANKCASE PRESSURE SIGNAL CIRCUIT OPEN
1. Measure the resistance of the (K926) Crankcase Pressure Signal circuit from the Crankcase Pressure Sensor harness connector and the ECM harness connector.

Is the resistance less than 10.0 Ohms?

Yes

- Go To 8

No

- Repair or replace the open wiring harness.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

8. (F855) 5-VOLT SUPPLY CIRCUIT OPEN
1. Measure the resistance between the (F855) 5-volt Supply circuit in the Crankcase Pressure Sensor harness connector with the (F855) 5-volt supply circuit in the ECM harness connector.

Is the resistance less than 10.0 Ohms?

Yes

- Go To 9

No

- Repair or replace the open wiring harness.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

9. (K926) CRANKCASE PRESSURE SIGNAL CIRCUIT SHORTED TO GROUND
1. Measure the resistance between the (K926) Crankcase Pressure Signal circuit in the Crankcase pressure sensor connector and battery negative.

Is the resistance greater than 10k Ohms?

Yes

- Go To 10

No

- Repair or replace the shorted to ground wiring harness.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

10. (F855) 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
1. Measure the resistance between the (F855) 5-volt Supply circuit in the Crankcase pressure sensor connector and battery negative.

Is the resistance greater than 10k Ohms?

Yes

- Go To 11

No

- Repair or replace the shorted to ground wiring harness.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

11. ECM
1. While monitoring scan tool, use a jumper wire to connect the (F855) 5-volt supply circuit with the (K926) Crankcase Pressure Signal circuit at the sensor harness connector.

Does the scan tool show a P051D DTC?

Yes

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

No

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

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