What does P0234 mean?

Boost pressure is above the level the ECU commanded.

Why does the car go into limp mode with P0234?

To protect the engine and turbo from excess pressure, the ECU limits power.

Turbo and boost

P0234 — Turbocharger/Supercharger A Overboost Condition

The boost pressure measured by the sensor is higher than the target the ECU requested. Excess boost can damage the engine, so the ECU may cut power.

Severity: High

Common causes

Wastegate or variable-geometry actuator stuck closed
Faulty boost control (solenoid) valve or vacuum line
Faulty boost pressure or MAP sensor
Sticking turbo vanes
Intake or boost hose problem

Symptoms

Sudden power loss or limp mode
Surging or uneven power delivery
Possible whistling or unusual turbo noise
Check engine light

How to check

Check boost control solenoid, vacuum lines and the wastegate actuator movement
Compare actual and requested boost on a scan tool
Check the boost pressure sensor and the intake system
Inspect the turbo for sticking vanes or damage

Can you keep driving?

Not recommended. Overboost can stress the engine and turbo; use the car only to reach a workshop.

Frequently asked questions

What does P0234 mean?: Boost pressure is above the level the ECU commanded.
Why does the car go into limp mode with P0234?: To protect the engine and turbo from excess pressure, the ECU limits power.

General reference information. It does not replace a diagnosis on your own vehicle. The same code can have different causes depending on make, model year and engine; check the manufacturer's documentation or ask a technician with a scan tool.