P2CB8Turbocharger/Supercharger Boost Pressure B Too High - Mechanical
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- P2CB8 reports that the second charger, B, produces more boost than the engine module allows, and attributes this to a mechanical cause such as a wastegate or bypass of charger B that no longer opens, a seized actuator rod or sooted variable vanes stuck in the closed position. It is the B twin of P226B. No manufacturer documents P2CB8 publicly. GM's A-side performance check on 2018 diesels watches the same overboost direction with a barometric correction and lists exhaust restrictions as a trigger. CARB requires overboost detection on boosted engines. Unlike P02CA, which only notes boost above target, P2CB8 points at hardware. To protect the turbine and engine, the module usually cuts torque or opens a relief path.
- What you may notice
- Sudden power cut under full load
- MIL on
- Surging or jerky boost build-up
- Likely causes
- LikelyWastegate of charger B stuck closed
- PossibleVariable turbine vanes of charger B sooted and sticking
- PossibleSeized actuator rod or linkage on charger B
- RareBoost pressure sensor B reading too high
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €100 – €3,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.