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P051C






P051C-CRANKCASE PRESSURE SENSOR CIRCUIT LOW





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.





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

1. OTHER DTCs
1. Ignition on, engine not running.
2. 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

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test

3. CHECK THE (F857) 5-VOLT SUPPLY CIRCUIT
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. Measure the voltage across the (F857) 5-Volt supply circuit and the (K916) Sensor Return circuit at the Crankcase Pressure Sensor harness connector.

Is the voltage between 4.5 and 5.5 Volts?

Yes

- Go To 4

No

- Go To 6

4. CHECK THE CRANKCASE PRESSURE SENSOR




1. While monitoring scan tool, use a jumper wire to connect the (F857) 5-Volt supply circuit with the (K926) Crankcase Pressure Signal circuit at the Crankcase Pressure Sensor harness connector.

Does the scan tool show a P051D DTC?

Yes

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

No

- Go To 5

5. CHECK FOR THE (K926) CRANKCASE PRESSURE SIGNAL CIRCUIT SHORTED TO THE (K916) SENSOR RETURN CIRCUIT




1. Turn the ignition off.
2. Remove the jumper wire.
3. Disconnect the PCM C1 harness connector.

NOTE: Check connectors - Clean/repair as necessary.

4. Turn the ignition on.
5. Measure the resistance between the (K926) Crankcase Pressure Signal circuit and (K916) Sensor Return circuit in the Crankcase Pressure Sensor harness connector.

Is the resistance above 10k Ohms?

Yes

- Go To 6

No

- Repair the short between the (K926) Crankcase Pressure Signal circuit and (K916) Sensor Return circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

6. CHECK FOR THE (F857) 5-VOLT SUPPLY CIRCUIT SHORTED TO THE (K916) SENSOR RETURN CIRCUIT




1. Turn the ignition off.
2. Measure the resistance between the (F857) 5-Volt Supply circuit and (K916) Sensor Return circuit at the Crankcase Pressure Sensor harness connector.

Is the resistance above 10k Ohms?

Yes

- Go To 7

No

- Repair the short between the (F857) 5-Volt Supply circuit and (K916) Sensor Return circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

7. CHECK THE (K926) CRANKCASE PRESSURE SIGNAL CIRCUIT FOR AN OPEN/HIGH RESISTANCE




1. 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 8

No

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

8. CHECK THE (F857) 5-VOLT SUPPLY CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Measure the resistance of the (F857) 5-Volt Supply circuit between the Crankcase Pressure Sensor harness connector and the PCM C1 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 9

No

- Repair the (F857) 5-Volt Supply circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

9. CHECK THE (K926) CRANKCASE PRESSURE SIGNAL CIRCUIT FOR A SHORT TO GROUND




1. Measure the resistance between ground and the (K926) Crankcase Pressure Signal circuit at the Crankcase Pressure Sensor harness connector.

Is the resistance above 10k Ohms?

Yes

- Go To 10

No

- Repair the (K926) Crankcase Pressure Signal circuit for a short to ground.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

10. POWERTRAIN CONTROL MODULE
1. While monitoring scan tool, use a jumper wire to connect the (F857) 5-Volt supply circuit with the (K926) Crankcase Pressure Signal circuit at the Crankcase Pressure Sensor harness connector.

Does the scan tool show a P051D DTC?

Yes

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test

No

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

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