P051B

P051B-CRANKCASE PRESSURE SENSOR CIRCUIT RANGE/PERFORMANCE





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, or during engine operation the crankcase pressure reading is not changing with engine operating conditions.







Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Initial Inspection and Diagnostic Overview


Diagnostic Test


1. OTHER DTCS
Turn the ignition on
Wait 5 seconds after ignition is turned on.
With the scan tool, read DTCs.
Is DTC P051D or P051C active?

Yes


- Troubleshoot other DTCs first.


No


- Go To 2



2. P051C ACTIVE
Turn the ignition off.
Disconnect the crankcase pressure sensor harness connector.

NOTE: Check connectors - Clean/repair as necessary.

Turn the ignition on.
With the scan tool, read DTCs.
Is DTC P051C active?

Yes


- Go To 3


No


- Go To 5



3. P051D ACTIVE
Connect a jumper wire between the crankcase pressure (F855) 5-volt supply circuit and the (K926) Crankcase Pressure Signal circuit at the crankcase pressure sensor harness connector.
With the scan tool, read DTCs.
Is DTC P051D active?

Yes


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


No


- Go To 4



4. CRANKCASE VENTED TO ATMOSPHERE
Inspect engine for crankcase leaks of oil or crankcase gases.
Check:
- Valve cover gasket.
- Crankcase breather tube.
- Dipstick tube.
- Block plugs.
- Oil fill cap.

Are any leaks found?

Yes


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


No


- Go To 5



5. ECM
Turn the ignition off.
Disconnect the (C1) ECM harness connector.

NOTE: Check connectors - Clean/repair as necessary.

Dirty or damaged pins?

Yes


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


No


- Go To 6



6. ECM
Turn the ignition off.
Connect a jumper wire between the crankcase pressure (F855) 5-volt supply circuit and the (K926) Crankcase Pressure Signal circuit at the crankcase pressure sensor harness connector.
Turn the ignition on.
With the scan tool, read DTCs.
Is DTC P051D active?

Yes


- High resistance or a short circuit has been detected in the engine harness. Repair/replace engine harness.


No


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