What it means
The third bypass valve has reached over-temperature. Either coil duty cycle is too high for too long, or cooling air flow around the valve is restricted.
At a glance
- Usually lights the check-engine light
How it works
Bypass valve C is the third valve used to manage air around the turbocharger or supercharger. The control module detects that this valve has become hotter than its allowed range, potentially because it has been driven at high duty for too long or because cooling airflow around it is restricted.
Common causes
Most likely first.
- Sustained high duty cycle from charge balancing strategy
- Cooling air channel blocked by debris
Symptoms
- Reduced engine power or boost
- Check-engine light may illuminate
How to diagnose it
- Read freeze-frame data and available valve temperature and duty-cycle values to see whether high commanded activity coincided with the over-temperature.
- Inspect the cooling-air path around valve C for debris, blocked openings, or damaged ducting.
- Check valve C's connector and wiring for heat damage that could affect its operation or temperature reading.
- Use a scan-tool actuator test, if supported, to check whether valve C responds normally without remaining heavily commanded.
- If airflow and wiring are intact, compare temperature-sensor and control data with the manufacturer's specification to distinguish a real overheat from an inaccurate reading.
Common fixes
- Clear debris from the cooling-air path around bypass valve C.
- Repair damaged ducting or wiring near valve C.
- Replace a confirmed faulty valve C temperature-sensing element or valve assembly.
- Address a verified control strategy or driver fault if testing shows it is keeping valve C energized excessively.
Can I keep driving?
Avoid hard acceleration, towing, and sustained boost until the cause is checked, especially if power is reduced or a temperature warning appears. Stop driving if an engine temperature warning occurs or the engine begins to overheat.
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.