Powertrain, generic · Fuel and air metering, auxiliary emission controls

P00C4 Turbocharger/Supercharger Bypass Valve B - Mechanical

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

Bypass valve B is the compressor recirculation (diverter) valve of turbocharger B, not the wastegate: it lets charge air flow back to the compressor inlet when the throttle closes quickly, so the compressor does not surge. Turbocharger B is the second turbocharger in exhaust flow on series systems and the turbocharger of bank 2 on parallel twin-turbo engines. P00C4 reports that the valve stays mechanically closed. A documented method detects this on overrun from the pulsation of the measured air mass that compressor surge causes when the valve should open.

Likely causes

Valve stuck closed or coked
Diaphragm or piston worn
Valve not actuated correctly
Consequence of a boost or air flow fault

Symptoms

  • Check engine light on
  • Fluttering or surging noise when lifting off the throttle
  • Boost fluctuations, loss of power

Repair estimate

DifficultyMediumDIY possible
Parts and labour€60–350
Time0.5–2 h

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

Parts involved

turbocharger bypass valve bturbocharger

Related codes

P00C3P00C0P2261P0234

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