P051B

P051B-CRANKCASE PRESSURE SENSOR CIRCUIT RANGE/PERFORMANCE





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

Theory of Operation

The Crankcase Pressure Sensor is used to monitor the pressure inside the crankcase. The Powertrain Control Module (PCM) 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 PCM monitors the crankcase pressure signal circuit voltage to calculate the pressure of the air within the crankcase. The PCM 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.

Is DTC P051D or P051C active?

Yes

- Troubleshoot other DTCs first.

No

- Go To 2

2. CHECK FOR 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 PCM C1 harness connector.

NOTE: Check connectors - Clean/repair as necessary.

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

Is the resistance below 5.0 Ohms?

Yes

- Go To 4

No

- Repair the (K926) Crankcase Pressure Signal 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 PCM C1 harness connector.
2. Turn the ignition on.
3. 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.
4. With the scan tool, read DTCs.

Is DTC P051C active?

Yes

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

No

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