P0234: Turbocharger/Supercharger "A" Overboost Condition

What does P0234 mean?

Turbocharged and supercharged engines regulate boost with a wastegate or bypass and a boost control system. The ECM watches boost with a pressure sensor. When boost goes over its limit, it stores P0234 and often reduces power.

Both references list boost control parts as common causes. RepairPal also lists the boost sensor and its wiring, and YourMechanic the wastegate, its control solenoid and the control hose.

Common symptoms

• Check engine light on
• Reduced power or limp mode
• Hesitation or stalling in some cases
• Possible engine knock under load

Common causes

The causes below are the ones commonly seen with P0234. The actual cause can vary by vehicle, engine and mileage, so treat this list as a starting point, not a diagnosis.

• A sticking or damaged wastegate
• A faulty boost control solenoid or blocked control hose
• A faulty boost pressure sensor or its wiring
• A faulty boost actuator

What to check with a scanner

• In Live data, watch boost or manifold pressure during gentle acceleration and compare it with the expected value for your engine.
• Check the boost pressure sensor connector and the control hoses for damage.
• Note companion codes such as P0299 or boost sensor codes.
• Read freeze frame data to see rpm and load when the code set.

How to read and clear P0234 with OBD Master Pro

1. Plug in your adapter. Connect a generic ELM327 (or ELM329) OBD2 adapter to the diagnostic port, usually under the dashboard on the driver's side. Bluetooth Classic, Bluetooth LE, Wi-Fi and USB OTG adapters are supported.
2. Switch the ignition on. Turn the key to ON or start the engine, depending on your car.
3. Connect in OBD Master Pro. Open the app, go to Connection and pick your adapter. Classic Bluetooth adapters connect from the Bluetooth tab, Bluetooth LE adapters from the BLE tab with no pairing needed. Use the generic OBD2 / EOBD profile or your car's brand profile.
4. Read the codes. Open the fault codes screen to see stored, pending and permanent codes. Confirm P0234 is listed and note any other codes, since they often explain the cause.
5. Check the details. Look at freeze frame data, Live data and, where your car supports it, Mode 06 test results (see the checks above).
6. Fix, then clear. After the repair, clear the codes to turn off the check engine light. Clearing also resets the emissions readiness monitors, so drive normally and check the readiness screen before any inspection. Permanent codes cannot be erased with a scan tool; they clear on their own once the car's self test passes.

Tip: you can also look up P0234 and other codes in the app's DTC search without connecting to a car. If your adapter will not connect, use Connection > Share connection log and email it to support. Many cheap ELM327 clones only handle basic engine OBD2, which is all you need for P0234.

When to see a mechanic

Get professional help if any of these apply:

• The engine goes into limp mode
• You hear knocking under load
• The wastegate or actuator needs testing

If you are unsure, a qualified technician can confirm the cause with tests such as smoke testing, pressure testing or scope readings. Clearing a code does not repair the fault.

Related trouble codes

See all OBD2 trouble code guides

Related guides

Check engine light on: what to do · How to read an OBD2 code (P, B, C, U) · Stored, pending and permanent codes and freeze frame · OBD2 readiness monitors explained · OBD2 glossary · OBD2 by car brand