P0238: Turbo boost pressure sensor A: high signal
The ECU sees a voltage that is too high from the turbo boost pressure sensor, usually a bad sensor earth, a damaged wire or the sensor itself.
| Code | P0238 |
|---|---|
| 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 P0238 means
The boost pressure sensor measures how hard the turbo is pushing air into the engine, and the ECU uses that reading to control the turbo. Which sensor counts as A is defined by each manufacturer. Here the ECU is receiving a voltage above anything the sensor should produce, which almost always means an electrical fault: wire, connector, earth or the sensor.
Most common causes
- Broken sensor earth wire or poor contact at the connector
- Signal wire touching the 5 volt supply or another live wire
- Corroded or damp connector
- Faulty boost pressure sensor
- Faulty engine ECU, which is rare
Symptoms
- Engine warning light on
- Loss of power or limp mode
- Turbo feels weak or uneven
- Higher fuel use, or black smoke on diesels
Can you drive with P0238?
With care You can drive, but the engine will often go into limp mode with reduced power. Drive gently and get it looked at soon.
Open the bonnetthe in-depth explanation
How to check it
With the ignition on and the engine off, the reader should show roughly atmospheric pressure (around 100 kPa at sea level). If it shows something very different, or the value does not move when you accelerate, suspect the sensor or its wiring.
How to read and clear P0238 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 P0238 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
- P0234 Turbocharger or supercharger A overboost
- 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
- P0239 The turbocharger boost sensor B has an electrical fault
- P023A The intercooler coolant pump control has a broken or disconnected wire
- P023B The intercooler coolant pump control gives a lower signal than normal
- P023C The intercooler coolant pump control gives a higher signal than normal
- 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 P0238 mean?
The boost pressure sensor measures how hard the turbo is pushing air into the engine, and the ECU uses that reading to control the turbo. Which sensor counts as A is defined by each manufacturer. Here the ECU is receiving a voltage above anything the sensor should produce, which almost always means an electrical fault: wire, connector, earth or the sensor.
Can you drive with P0238?
You can drive, but the engine will often go into limp mode with reduced power. Drive gently and get it looked at soon.
How do you clear P0238?
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, P0238 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.
