Turbo/Supercharger Bypass Valve Control Circuit Range/Performance
Code P0039 indicates that the Powertrain Control Module (PCM) has detected a malfunction in the bypass valve control circuit for the turbocharger or supercharger. This valve regulates boost pressure by diverting exhaust gases away from the turbine. The PCM monitors the circuit for voltage, resistance, or performance issues. A fault can cause improper boost control, leading to reduced engine power, poor fuel economy, and potential damage to the turbocharger or engine.
01. Most Common Causes
- Faulty bypass valve solenoid
- Wiring or connector issues in the control circuit
- Carbon buildup or mechanical sticking of the bypass valve
- Failed PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine power or hesitation during acceleration
- Poor fuel economy
- Possible turbocharger overboost or underboost
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect the bypass valve, wiring, and connectors for damage or corrosion.
Step 3: Test the bypass valve solenoid resistance and compare to manufacturer specs.
Step 4: Check for proper voltage and ground at the solenoid connector with a multimeter.
Step 5: Perform a bypass valve actuation test using a scan tool to verify operation.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as it can cause reduced performance and potential damage to the turbocharger or engine. Seek repair promptly.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on the cause and vehicle model.