P1508

P1508-CRANKCASE FILTER RESTRICTION - REPLACE FILTER

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:
Engine speed greater than 500 RPM and engine temperature is above 82°C (180°F) for five minutes.

- Set Condition:
The Powertrain Control Module (PCM) detects the crankcase pressure exceeds a calibrated limit.





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

1. CRANKCASE OBSTRUCTIONS
1. Disconnect the crankcase outlet hose.

Are there any obstructions in the crankcase outlet hose or port?

Yes

- Clear the obstructions.
- Go To 2

No

- Go To 2

2. CRANKCASE DEPRESSION VALVE

Is the Crankcase Depression Valve stuck shut?

Yes

- Replace the Breather Filter Cover (the Crankcase Depression Valve is a part of this cover and is not serviceable). Check the system for any progressive damage due to excessively low crankcase pressures.
- Go To 3

No

- Go To 3

3. DTC ACTIVE
1. Ignition on, engine not running.
2. With the scan tool, read DTCs.

Is fault code P1508 active?

Yes

- Replace the crankcase breather filter and check for progressive engine damage due to high crankcase pressures.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Clear the DTC, repair complete.