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 |
|---|---|
| System | Engine and transmission |
| Group | P02xx, Fuel and injectors |
| Type | Generic: 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.
Open the bonnetthe in-depth explanation
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 its description and whether it’s confirmed, pending or permanent.
If the engine stores it over standard OBD, with FREE you read this code with its explanation for nothing and clear it. With PRO you also read the faults of every control unit and clear them in all of them.
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 an inspection. It’s all in how to read and clear fault codes and in inspections and OBD.
Similar codes
- P0230 Fuel pump primary circuit malfunction
- P0231 Fuel pump secondary circuit low
- P0232 Fuel pump secondary circuit: high signal
- P0233 The fuel pump relay circuit has an intermittent fault
- P0235 Turbo boost pressure sensor A: circuit fault
- P0236 Turbo boost pressure sensor A: range or performance problem
- P0237 Turbo boost pressure sensor A: low signal
- P0238 Turbo boost pressure sensor A: high signal
- P0200 Injector circuit malfunction
- P0201 Injector circuit malfunction, cylinder 1
- P0202 Injector circuit malfunction, cylinder 2
- P0203 Injector circuit malfunction, cylinder 3
To understand it properly
We explain how that system works, with drawings and no waffle, in our mechanics guide: Turbo and intercooler.
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.
Read it on your car
Final OBD reads and clears engine faults through standard OBD for free, each one explained in plain English. With PRO it also reads the faults of every control unit, each make’s own codes included, and clears them in all of them.
