Turbo Charger Bypass Valve Control Circuit
Code P0033 means the PCM has detected a fault in the turbocharger or supercharger bypass valve control circuit. The bypass valve (also called a diverter valve or blow-off valve) releases pressurized intake charge back into the intake to protect the turbo during throttle lift-off. P0033 indicates an open or short in the electrical circuit controlling this valve — the valve itself may still be mechanically functional.
What You Might Notice
- Check engine light on
- Possible boost-related hesitation on acceleration
- Turbo flutter or compressor surge sound during throttle lift-off
- Slight reduction in boosted performance
Most Common Causes
- 1
Failed bypass valve solenoid
The solenoid controlling the bypass valve has an open or shorted coil. Test resistance — typically 20–40 ohms depending on application.
- 2
Open or short in bypass valve control wiring
The wiring harness to the bypass valve solenoid has a break or short. Inspect near boost pipes and heat sources.
- 3
Corroded solenoid connector
Corrosion in the bypass valve connector creates circuit resistance that triggers a fault.
How to Diagnose It
- 1
Check Failed bypass valve solenoid — The solenoid controlling the bypass valve has an open or shorted coil. Test resistance — typically 20–40 ohms depending on application.
- 2
Check Open or short in bypass valve control wiring — The wiring harness to the bypass valve solenoid has a break or short. Inspect near boost pipes and heat sources.
- 3
Check Corroded solenoid connector — Corrosion in the bypass valve connector creates circuit resistance that triggers a fault.
How to Fix It
- 1
Inspect bypass valve solenoid connector and wiring
Check for corrosion in the connector and damage in the harness near boost pipes.
- 2
Test solenoid resistance
Disconnect and measure resistance. Replace if open, shorted, or out of spec.
- 3
Replace the bypass valve solenoid
Install a quality replacement bypass valve/solenoid assembly.
- 4
Clear codes and verify
Confirm circuit is operational after repair.
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