What it means
The turbocharger/supercharger bypass valve B reports a stuck condition. Boost recirculation cannot be commanded reliably on this branch.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
- The engine or gearbox may go into limp mode
How it works
A turbocharger or supercharger bypass valve B opens or closes a recirculation path to manage boost on its branch. The control module compares the commanded valve action with its response and sets P2C29 when valve B is detected as stuck, so boost cannot be controlled reliably.
Common causes
Most likely first.
- Bypass valve mechanically seized
- Carbon deposits jam the valve
Symptoms
- Check engine light on
- Significant power loss / limp mode
- Possible blue or black smoke from exhaust
- Whistling or hissing sound from intake
How to diagnose it
- Read freeze-frame data and scan-tool boost and bypass-valve command data to see when valve B fails to respond.
- With the engine off and cool, inspect bypass valve B, its linkage and nearby intake hoses for obstruction, damage or signs the valve cannot move freely.
- Check the valve B connector and wiring for loose pins, corrosion or damage that could mimic a mechanically stuck valve.
- If the scan tool supports it, command bypass valve B through its operating range and compare the reported position or boost response with the command.
- If the valve is accessible, check for deposits or mechanical seizure and confirm that the actuator and valve move as specified by the manufacturer.
Common fixes
- Remove an obstruction or clean deposits from bypass valve B if the manufacturer's service procedure permits it.
- Repair a leaking or disconnected hose on the valve B recirculation branch.
- Repair damaged wiring or connector terminals to bypass valve B.
- Replace a seized bypass valve B or failed actuator after confirming the mechanism is stuck.
Can I keep driving?
With marked power loss or limp mode, avoid overtaking, towing and steep or high-speed driving; boost may be limited or unpredictable. Stop if smoke is heavy, the engine runs badly, or a loud intake leak develops, as continued operation can worsen engine or turbocharger damage.
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.