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P0234: Turbocharger or supercharger A overboost

The turbo or supercharger is producing more boost than allowed. The cause is usually the wastegate, its control solenoid or its vacuum hoses.

Code P0234 at a glance
CodeP0234
SystemEngine and transmission
GroupP02xx, Fuel and injectors
TypeGeneric: it means the same on every make
Can you keep driving?With care

What P0234 means

The turbo (or supercharger) forces extra air into the engine so it makes more power. The ECU has seen boost pressure go above its set limit, and which unit counts as turbo A is defined by each manufacturer. To protect itself, the engine usually goes into limp mode and cuts power.

Most common causes

  • Split, loose or misrouted vacuum hose to the wastegate
  • Faulty boost control solenoid or loose connector
  • Sticking wastegate or seized variable vane mechanism on the turbo
  • Boost pressure sensor reading too high
  • Blocked or kinked hose to the boost sensor
  • Modified engine software or an ECU fault

Symptoms

  • Engine warning light on
  • Sudden loss of power as the car enters limp mode
  • Surge of power in the mid range just before the cut
  • Louder than usual turbo whistle

Can you drive with P0234?

With care You can drive gently to a workshop without using full throttle. Sustained overboost can damage the turbo or the engine, so do not put it off.

How to check it

Use your reader to watch actual and requested boost live while accelerating in a high gear; if actual clearly overshoots, note it down. Also check by eye that the small vacuum hoses around the turbo are intact and properly fitted.

How to read and clear P0234 with Final OBD

Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P0234 with this same explanation and whether it’s confirmed, pending or permanent.

With Free you read this code with its short description for nothing, and clear it if the engine stores it over standard OBD. With Pro you get the full explanation, how the car was running when it was logged (revs, temperature, load) and clearing in every control unit.

Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before the ITV. It’s all in how to read and clear fault codes and in the ITV and OBD.

Similar codes

P0234 is a generic code, so it means the same on any make, for example on BMW, Ford, Mazda, Mercedes-Benz, Peugeot, Volkswagen. See what Final OBD does on your car in makes and models.

What does code P0234 mean?

The turbo (or supercharger) forces extra air into the engine so it makes more power. The ECU has seen boost pressure go above its set limit, and which unit counts as turbo A is defined by each manufacturer. To protect itself, the engine usually goes into limp mode and cuts power.

Can you drive with P0234?

You can drive gently to a workshop without using full throttle. Sustained overboost can damage the turbo or the engine, so do not put it off.

How do you clear P0234?

With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, P0234 comes back.