P0235
Turbocharger/Supercharger Boost Sensor A Circuit.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 2
- AreaFuel and air metering (injector circuit)
- 35
- FaultThe specific fault in that area
What it means
P0235 means the engine control unit has detected a fault in the circuit of boost pressure sensor A, which measures turbocharger or supercharger boost. The control unit saw a signal voltage outside the expected range, an implausible reading, or a reading that did not agree with other sensors such as the manifold or barometric pressure sensor. The exact trigger and sensor location vary by model and engine.
Symptoms
- Engine warning light on
- Loss of power or reduced boost
- Car goes into limp mode
- Poor or hesitant acceleration
- Black smoke or rough running under load
- Higher than normal fuel consumption
Possible causes
- Faulty boost pressure sensorlikely
- Damaged, chafed or corroded wiring to the sensor (signal, reference or earth)likely
- Loose, corroded or contaminated sensor connectorlikely
- Split, loose or blocked vacuum or boost hose to the sensor, or a boost leakpossible
- Sensor blocked by oil or soot depositspossible
- Fault in the engine control unitrare
How to diagnose
- Read all stored codes and freeze frame data to see engine load, speed and boost at the time the fault set, and note any other pressure sensor codes.
- Visually inspect the sensor, its connector and wiring for chafing, heat damage, corrosion, oil ingress or loose pins.
- Check the sensor's hose, seals and the intercooler pipework for splits, loose clamps and oil leaks.
- With the ignition on and engine off, compare the live boost sensor reading with barometric or manifold pressure readings; they should be close to ambient.
- Check the sensor's reference voltage and earth at the connector against the manufacturer's specification for that model.
- Check the signal wire for continuity and for shorts to earth or supply, with the connector and control unit disconnected.
- Compare live boost readings during a road test with the requested boost value to see whether the reading is plausible.
- Test or substitute the sensor only after wiring and supply checks are fine, following the manufacturer's procedure.
How to fix
- Replace the boost pressure sensor if its output is out of range or implausible.
- Repair or replace damaged wiring and clean or replace corroded connector terminals.
- Replace split or loose boost and vacuum hoses and refit clamps correctly.
- Clean or replace the sensor if it is contaminated, and find the cause of oil or soot reaching it.
- Diagnose and repair the control unit only after all other causes are ruled out, following the manufacturer's guidance.
Can I keep driving?
The car can usually be driven carefully for a short time, but limp mode and reduced power can make overtaking and junctions unsafe. Get it checked soon, as running with incorrect boost control can cause poor running and, in some cases, engine or turbocharger damage.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.