P051C

P051C-CRANKCASE PRESSURE SENSOR CIRCUIT LOW





For a complete wiring diagram Refer to Diagrams/Electrical.

Theory of Operation


The crankcase pressure sensor is used to monitor the pressure inside the crankcase. The 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. Initial Inspection and Diagnostic Overview


Diagnostic Test


1. OTHER DTCS
Ignition on, engine not running.
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


- Refer to the INTERMITTENT CONDITION - DIESEL Symptom. Intermittent Condition



3. INTERMITTENT CONDITION
Turn the ignition off.
Disconnect the Crankcase pressure sensor 1/1 harness connector.

NOTE: Check connectors - Clean/repair as necessary.

Measure the voltage from 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
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 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
Turn the ignition off.
Disconnect the ECM harness connector.

NOTE: Check connectors - Clean/repair as necessary.

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 100 k Ohms?

Yes


- Go To 6


No


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



6. (F855) 5-VOLT SUPPLY CIRCUIT SHORTED TO THE (K916) SENSOR GROUND
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 100 k Ohms?

Yes


- Go To 7


No


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



7. (K926) CRANKCASE PRESSURE SIGNAL CIRCUIT OPEN
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 ohms?

Yes


- Go To 8


No


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



8. (F855) 5-VOLT SUPPLY CIRCUIT OPEN
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 ohms?

Yes


- Go To 9


No


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



9. (K926) CRANKCASE PRESSURE SIGNAL CIRCUIT SHORTED TO GROUND
Measure the resistance between the (K926) Crankcase Pressure Signal circuit in the Crankcase pressure sensor connector and battery negative.
Is the resistance greater than 100 k Ohms?

Yes


- Go To 10


No


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



10. (F855) 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
Measure the resistance between the (F855) 5-volt Supply circuit in the Crankcase pressure sensor connector and battery negative.
Is the resistance greater than 100 k Ohms?

Yes


- Go To 11


No


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



11. ECM
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


- Refer to the INTERMITTENT CONDITION - DIESEL Symptom. Intermittent Condition


No


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