OBD-II · Engine and powertrain (P)
P0234
Turbocharger overboost condition
What it means
Boost pressure has gone above the engine computer's target, so it usually cuts power to protect the engine.
Symptoms
- sudden loss of power (limp mode) under hard acceleration, often clearing after a restart
- engine warning light
Likely causes, most likely first
| No. | Cause |
|---|---|
| 01 | sticking variable turbine vanes (soot build-up) |
| 02 | boost control solenoid or electronic actuator fault |
| 03 | vacuum hose split or wrongly routed on vacuum-controlled turbos |
| 04 | boost pressure sensor reading wrong |
| 05 | non-standard engine software (remap) |
What to check, step by step
- 01Read live data: requested vs actual boost; with engine off, boost reading should match atmospheric pressure.
- 02Check the turbo actuator moves freely through its full travel.
- 03Test the boost control solenoid and inspect vacuum lines.
- 04Check for non-standard engine software.
- 05If the vanes stick, have the turbo mechanism inspected and repaired or reconditioned. Avoid hard acceleration and high load until the overboost fault is diagnosed; do not try to clear it with a hard drive.