What it means
The control circuit of the electrically actuated PCV regulator valve has an open circuit. The ECU cannot adjust crankcase ventilation flow against engine load - typically affects emissions and oil consumption under high load.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The PCV regulator valve controls crankcase ventilation flow, and its electrical control circuit lets the engine controller adjust that flow as operating conditions change. P05D8 sets when the controller detects an open circuit, so it may be unable to command the valve as intended.
Common causes
Most likely first.
- Open in valve or harness
- Pin pushed back out of connector body
- Cracked solder joint inside the module or sensor
Symptoms
- Check-engine light may illuminate
- Crankcase ventilation or emissions fault may be indicated
How to diagnose it
- Use a scan tool to check freeze-frame data and any PCV regulator valve command or circuit codes for clues about when the open was detected.
- Inspect the PCV regulator valve connector and nearby harness for disconnection, corrosion, damage, or a pushed-back terminal.
- Check the harness for a broken wire or poor connection between the valve and controller, using the wiring diagram.
- With power isolated as specified in service information, test circuit continuity and check the valve winding or actuator against the manufacturer's specification.
- If the valve and wiring pass, inspect the controller connector and test its driver circuit using the manufacturer's procedure.
Common fixes
- Reconnect the PCV regulator valve or restore a loose or pushed-back connector terminal.
- Repair an open or damaged wire in the valve control circuit.
- Replace the PCV regulator valve if its electrical test confirms an internal open.
- Repair a confirmed open or failed driver circuit in the controller.
Can I keep driving?
A short, gentle trip is generally reasonable if the engine runs normally, but arrange diagnosis soon because ventilation control and emissions can be affected. Avoid heavy load if the engine develops rough running, unusual oil use, or other worsening symptoms.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.