P051B

P051B-CRANKCASE PRESSURE SENSOR CIRCUIT RANGE/PERFORMANCE







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:
At key on, engine not running the Crankcase Pressure Sensor reading is higher than a calibrated threshold, or during engine operation the crankcase pressure reading is not changing with engine operating conditions.





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

1. OTHER DTCS
1. Turn the ignition on.
2. Wait five seconds after ignition is turned on.
3. With the scan tool, read DTCs.

Are the P051D or P051C DTCS active?

Yes

- Troubleshoot other DTCs first.

No

- Go To 2

2. CRANKCASE VENTED TO ATMOSPHERE
1. Inspect engine for crankcase leaks of oil or crankcase gases.
2. Check the valve cover gasket, crankcase breather tube, dipstick tube, block plugs, and oil fill cap.

Are any leaks found?

Yes

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

No

- Go To 3

3. CHECK FOR HIGH RESISTANCE IN THE (K926) CRANKCASE PRESSURE SENSOR SIGNAL CIRCUIT
1. Turn the ignition off.
2. Disconnect the Crankcase Pressure Sensor harness connector.
3. Disconnect the ECM C1 harness connector.
4. Measure the resistance of the (K926) Crankcase Pressure Sensor Signal Sensor circuit between the Crankcase Pressure Sensor harness connector and the ECM C1 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 4

No

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

4. CHECK THE CRANKCASE PRESSURE SENSOR
1. Reconnect the ECM C1 harness connector.
2. Turn the ignition on.
3. With the scan tool, read DTCs.
4. Connect a jumper between the (K926) Crankcase Pressure Sensor Signal Sensor circuit and the (F855) 5-Volt Supply circuit at the Crankcase Pressure Sensor harness connector.

Is DTC P051C active with the connector unplugged and P051D active with the jumper in place?

Yes

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

No

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