What it means
Bypass valve B control voltage below expected range — short to ground. Boost control tracks commanded vs. actual manifold pressure; persistent deviation means wastegate, vanes, hose or actuator are not delivering the requested pressure.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Bypass valve B controls airflow around a turbocharger or supercharger compressor, and the control module monitors the electrical circuit that operates it. P00C1 sets when the valve B control voltage is below the expected range, commonly because the circuit is shorted to ground. This is an electrical low condition, not a general boost-pressure reading.
Common causes
Most likely first.
- Wiring shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Charge status indicator shows fault
- Charging may not start or interrupts
- Slower-than-expected charge rate
How to diagnose it
- Read freeze-frame data and related codes to confirm the fault is for bypass valve B's low control voltage rather than another boost-control component.
- Locate valve B and inspect its harness for chafing, pinched insulation, or contact with ground, especially near brackets and hot or moving parts.
- Check valve B's connector for corrosion, loose pins, moisture, or damaged terminals that could lower circuit voltage.
- With the circuit tested safely, measure the control signal and check for an unintended short to ground using the manufacturer's specification.
- If wiring is intact, test the valve B actuator and module control circuit according to the manufacturer's procedure.
Common fixes
- Repair chafed or pinched valve B wiring that is shorting to ground.
- Clean and secure corroded or loose connector terminals, replacing damaged terminals as needed.
- Replace a bypass valve B solenoid or actuator if it is internally shorted and testing confirms the fault.
- Repair a confirmed control-circuit fault at the module connector.
Can I keep driving?
Use gentle throttle and avoid high boost until valve B's circuit is repaired, since boost control may not respond as intended. Stop if the vehicle loses power unpredictably or develops unusual turbocharger or supercharger noises.
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.