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 will illuminate the MIL lamp after the monitor runs and fails in two consecutive trips.

- When Monitored:
This monitor is run under two different conditions. First is with the ignition on, engine not running. The second is a comparison check with the engine running. This monitor runs five minutes after the coolant temperature reaches 82°C (180°F).

- 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.
NOTE: If the fault is set due to condition one, the environmental data will show zero for the engine speed.





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. Turn the ignition off.
2. Inspect engine for crankcase leaks of oil or crankcase gases.
3. 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 ICE BUILD UP IN THE CRANKCASE VENTILATION SYSTEM
1. Turn the ignition on.
2. With the scan tool, erase DTCs.
3. Start the engine and allow the coolant temperature to reach 82°C (180°F), then idle for at least five minutes.
4. With the scan tool, read DTCs.

Did the DTC return?

Yes

- Go To 4

No

- Repair complete. Fault was due to ice build up in the crankcase ventilation system.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

4. P051C ACTIVE
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. With the scan tool, read DTCs.

Is DTC P051C active?

Yes

- Go To 5

No

- Go To 5

5. P051D ACTIVE
1. Connect a jumper wire between the (F855) 5-Volt Supply circuit and the (K926) Crankcase Pressure Signal circuit at the Crankcase Pressure Sensor harness connector.
2. With the scan tool, read DTCs.

Is DTC P051D active?

Yes

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

No

- Go To 6

6. PCM HARNESS INSPECTION
1. Turn the ignition off.
2. Disconnect the PCM C1 harness connector.
3. Visually inspect the PCM C1 harness connector.

NOTE: Check connectors - Clean/repair as necessary.

Dirty or damaged pins?

Yes

- Replace/repair the PCM or engine harness.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 7

7. POWERTRAIN CONTROL MODULE
1. Turn the ignition off.
2. Measure the resistance of the:
- (F855) 5-Volt Supply circuit between the Crankcase Pressure Sensor harness connector and the PCM C1 harness connector.
- (K926) Crankcase Pressure Sensor Signal circuit between the Crankcase Pressure Sensor harness connector and the PCM C1 harness connector.
- (K16) Crankcase Pressure Sensor Return circuit between the Crankcase Pressure Sensor harness connector and the PCM C1 harness connector.

Is the resistance below 5.0 Ohms for each circuit?

Yes

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

No

- High resistance has been detected in the engine harness. Repair/replace engine harness.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.