P2C29Turbocharger/Supercharger Bypass Valve B Stuck
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- Bypass valve B is the compressor recirculation valve of the second charger – the later one in series layouts, the bank 2 unit on parallel twin-turbo engines. It is not the wastegate. P2C29 means a position-controlled valve no longer follows its target and stays where it is. No manufacturer documents P2C29 publicly. The A-side twin P23AA shows the method on GM's 2019 Corvette LT5: a position error above 25 % lasting at least 1 s while the valve barely moves (under 10 %/s), 10 of 14 samples, Type A. GM's 2019 CT6 4.2L twin-turbo, by contrast, uses switched dump valves without a sensor for both banks and reports a sticking valve B as P00C4. Stuck closed causes surge noise on lift-off; stuck open costs boost.
- What you may notice
- Check engine light
- Less boost and power
- Fluttering compressor noise when lifting off
- Likely causes
- LikelyOil or carbon deposits binding the valve flap or piston
- PossibleWorn gears or motor in the electric actuator
- RareBent shaft or damaged housing of the valve
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €150 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.