HomeTrouble CodesP0033

P0033 — Turbochargersupercharger Bypass Valve Control Circuit

Generic OBD-II · all makesPowertrain (engine & transmission)

This code indicates the powertrain control module has detected an electrical malfunction in the circuit controlling the turbocharger or supercharger bypass valve (also called a recirculation or blow-off valve). The valve regulates boost pressure by diverting excess airflow, and the fault may involve an open circuit, short to ground or power, or an abnormal voltage reading.

Symptoms

What causes it — most likely first

1. Faulty bypass valve solenoid or actuator

The electromagnetic coil or motor actuator that physically moves the valve has failed internally, preventing proper electrical operation and causing circuit voltage readings outside expected parameters.

2. Wiring harness damage or corrosion

Open circuits, shorts to ground or voltage, or high resistance in the wiring between the PCM and valve connector due to chafing, heat damage, rodent chewing, or moisture intrusion.

3. Poor electrical connections

Corroded, bent, backed-out, or loose pins in the valve connector or related harness connectors causing intermittent or permanent circuit failure.

4. Vacuum line obstruction or leak

For vacuum-actuated bypass valves, cracked hoses, loose fittings, or blockages prevent proper valve operation and may trigger circuit monitoring faults in integrated solenoid systems.

5. Failed PCM (rare)

Internal driver circuit failure within the powertrain control module is uncommon for this specific code; this should only be considered after all wiring and component testing confirms integrity.

How it's diagnosed

  1. Visually inspect the bypass valve wiring harness and connector for corrosion, damage, pin push-out, or loose connections.
  2. Check vacuum hoses (if equipped) for cracks, leaks, or disconnections affecting valve operation.
  3. Measure solenoid resistance with a multimeter and compare to manufacturer specifications; test actuator operation by applying direct power and ground.
  4. Monitor the control circuit with a scan tool or oscilloscope to verify PCM command signals and compare to actual valve response.
  5. Evaluate PCM operation only after confirming wiring integrity and component function, as module failure is an unlikely cause for this specific circuit fault.

Code facts & related codes

SystemPowertrain (engine & transmission)
StandardizationSAE generic — identical on every make

Frequently asked

Can I continue driving with this code?

Short trips are generally possible, but prolonged driving may cause turbocharger stress or catalytic converter damage due to improper boost regulation; repair should be scheduled promptly.

Does this mean my turbocharger needs replacement?

No, the code specifically indicates an electrical control circuit issue with the bypass valve rather than mechanical failure of the turbocharger itself.

My mechanic wants to replace the engine computer; is that necessary?

PCM failure causing this code is rare; insist on testing the wiring harness and valve solenoid first, as these components are far more commonly at fault.

What is the difference between a bypass valve and a wastegate?

A bypass valve (blow-off valve) typically recirculates or vents excess compressed air from the intake tract, while a wastegate diverts exhaust gases to control turbine speed; both regulate boost but operate in different parts of the system.