P0234 fault code: what it means

P0234: Turbo boost pressure has gone higher than the limit (overboost). Engine may cut power to protect itself.

Engine and gearbox (powertrain) · Costly if missed

Usual causes, most likely first

wastegate or turbo vanes stuck closed
faulty boost control solenoid
split or disconnected wastegate vacuum line
faulty boost pressure sensor

P0234 by make

Audi

Turbo overboost: boost pressure went above the limit. Often hoses routed wrong or a faulty boost control valve; a sticking turbo can also cause it.

Usual causes: boost or vacuum hoses damaged or routed wrong; faulty boost control valve (N75); faulty boost pressure sensor (G31); sticking turbo (VNT vanes or wastegate)

BMW

Turbo overboost: boost went higher than the DME asked for. On BMW petrol turbos usually the wastegate control.

Usual causes: wastegate stuck or rattling (N54); wastegate vacuum solenoid or hose fault; boost pressure sensor

Ford

Turbo overboost: boost went higher than the engine allows. Often set alongside P0299 when boost control is erratic.

Usual causes: sticking turbo vanes or actuator (diesel); faulty wastegate control solenoid (EcoBoost); boost pressure sensor fault

GWM

Turbo overboost.

Usual causes: sticking VGT vanes; boost control solenoid or vacuum hose; boost pressure sensor

Haval

Turbo overboost.

Usual causes: wastegate actuator sticking closed; boost pressure sensor; boost control fault

Hyundai

Turbo overboost: boost pressure higher than the ECM wants (1.6 / 2.0 T-GDI).

Usual causes: sticking or worn wastegate actuator or linkage; faulty boost control solenoid or its vacuum hoses; faulty boost pressure sensor

Isuzu

Turbo overboost.

Usual causes: sticking VGT turbo vanes; boost control (VGT) solenoid or vacuum hose; boost pressure sensor

Jeep

Turbo overboost on CRD diesels.

Usual causes: sticking turbo vanes or actuator; boost control solenoid or vacuum hose; boost pressure sensor

LDV

Turbo overboost.

Usual causes: sticking VGT vanes; boost control solenoid; boost pressure sensor

Mazda

SkyActiv-D: small turbo overboost. Boost is above target, usually the turbo regulating (bypass) valve control.

Usual causes: regulating solenoid valve; vacuum or pressure pipe to the regulating valve; regulating valve position sensor; MAP sensor No.2

Mercedes-Benz

Turbo overboost. On OM642 the electronic turbo vane actuator is often stuck or seized.

Usual causes: seized turbo vanes/actuator; faulty electronic turbo actuator; boost pressure sensor fault

Mini

Turbo overboost: boost higher than the DME asked for (Cooper S / JCW).

Usual causes: wastegate sticking; wastegate control solenoid or vacuum hose; boost pressure sensor

Mitsubishi

Turbo overboost (4D56 / 4N15 VGT). Boost went over the limit; ECU may cut power.

Usual causes: VGT vanes or actuator sticking (carbon); faulty boost control solenoid or vacuum hose; faulty MAP (boost) sensor; aftermarket tune or boost device

Nissan

Turbo overboost: boost went above the ECM limit. YD25 drops into limp mode.

Usual causes: boost control solenoid fault; sticking turbo vanes / actuator; vacuum hose fault; aftermarket tuning

Skoda

Turbo overboost: boost pressure went above the limit. Often hoses routed wrong or a faulty boost control valve; a sticking turbo can also cause it.

Usual causes: boost or vacuum hoses damaged or routed wrong; faulty boost control valve (N75); faulty boost pressure sensor (G31); sticking turbo (VNT vanes or wastegate)

Subaru

Turbo overboost: boost went above the limit (WRX, STI, Forester XT, Levorg, Liberty GT).

Usual causes: wastegate stuck closed or seized; faulty boost control solenoid; split or misrouted boost control hose; aftermarket tune or boost controller

Volkswagen

Turbo overboost: boost pressure went above the limit. Often hoses routed wrong or a faulty boost control valve; a sticking turbo can also cause it.

Usual causes: boost or vacuum hoses damaged or routed wrong; faulty boost control valve (N75); faulty boost pressure sensor (G31); sticking turbo (VNT vanes or wastegate)

Volvo

Turbo overboost: boost went above the limit. Seen on D5 diesels and T5 petrols.

Usual causes: sticking turbo vanes or wastegate; faulty boost control valve or actuator; boost pressure sensor

What the repair usually costs

CVT valve body replacement (remanufactured, in car)NZ$1,280–NZ$2,420 · A$1,200–A$2,400
A/C compressor replace incl. drier and flush (European)NZ$1,560–NZ$3,200 · A$1,490–A$3,050
Parking sensor replace, one sensorNZ$130–NZ$520 · A$130–A$510

Not sure what P0234 means on your car? Ask Credov.

Before you clear it

Write the code down or photograph the scanner first. A code that comes straight back after clearing points to a fault that is still there. A car whose codes were cleared just before you arrived may be hiding one: the scanner's readiness monitors show "not ready" for a while after codes are cleared.

Researched by Credov from manufacturer and workshop sources. A fault code points to where a fault may be; a workshop confirms it with a diagnosis. Browse all fault codes.