Powertrain, generic (extended)

P2C29 Turbocharger/Supercharger Bypass Valve B Stuck

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Oil or carbon deposits binding the valve flap or piston
Worn gears or motor in the electric actuator
Bent shaft or damaged housing of the valve

Symptoms

  • Check engine light
  • Less boost and power
  • Fluttering compressor noise when lifting off

Repair estimate

DifficultyHardWorkshop job
Parts and labour€150–1,200
Time1–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

turbo bypass valve bwiring harnessecm

Related codes

P23AAP00C4P2C2AP2C2DP2CD5P00C0

References: law.cornell.edu, gsi.ext.gm.com, gsi.ext.gm.com.