What it means
The control circuit for the turbocharger or supercharger bypass valve has a fault. The code does not by itself identify a mechanical valve problem.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
A turbocharger or supercharger bypass valve routes air around the compressor when boost is not needed or must be controlled. The engine module monitors the valve's electrical control circuit and sets P0033 when it detects a circuit fault; the code alone does not prove that the bypass valve itself is mechanically stuck.
Common causes
Most likely first.
- Faulty bypass valve control solenoid or actuator
- Open or shorted wiring
- Poor connector contact
Symptoms
- Check engine light on
- Reduced engine performance
How to diagnose it
- Save freeze-frame data and scan for boost-control or related electrical codes that may point to a shared power or wiring issue.
- Identify the bypass valve and inspect its connector and harness for loose connections, heat damage, chafing, or corrosion.
- Check any relevant fuse and verify that the valve connector terminals are seated and undamaged.
- Use the wiring diagram to test the bypass valve control circuit for opens or shorts, following the manufacturer's method for commanding or measuring the circuit.
- If the circuit wiring is sound, test the valve solenoid or actuator and its mechanical movement as specified for the vehicle.
Common fixes
- Reconnect the bypass valve plug and secure a loose harness.
- Repair damaged or shorted control-circuit wiring.
- Clean or replace poor connector terminals.
- Replace the bypass valve solenoid or actuator if circuit testing confirms it has failed.
Can I keep driving?
If the engine runs normally, a gentle trip may be possible, but avoid hard acceleration or towing because boost control and engine power may be reduced. Stop if the vehicle loses power unpredictably or develops severe running problems.
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.