P0236

What it means

P0236 means the engine control unit has found that the signal from boost pressure sensor A does not make sense for the current operating conditions. The sensor circuit is not necessarily open or shorted, but the reading is out of range or does not match expected values, such as the barometric reading at key-on or the manifold pressure compared with load and throttle position. The code points to a sensor, wiring, or boost pressure delivery problem, and the exact strategy varies by manufacturer and engine.

Symptoms

• Engine warning light on
• Loss of power or hesitation under acceleration
• Car going into limp mode with reduced boost
• Poor fuel economy
• Black or blue-grey smoke, or rough running in some cases
• Turbo whistling, hissing or surging noises if there is a boost leak

Possible causes

• Leak in the charge air system, such as a split hose, loose clamp or leaking intercooler, so boost is lower than the sensor or model expectslikely
• Faulty or contaminated boost pressure sensor giving a skewed or sluggish readinglikely
• Blocked, split or disconnected vacuum or pressure sensing hose to the sensor (where fitted)possible
• Damaged wiring, corroded connector terminals or high resistance in the sensor supply, earth or signal circuitpossible
• Turbo control fault, such as a sticking wastegate or variable geometry mechanism, or a faulty actuator or control solenoid, causing real boost to differ from targetpossible
• Restricted intake or exhaust, such as a blocked air filter or clogged exhaust components, affecting manifold pressurerare
• Fault in the engine control unit itself, or an outdated calibration where the manufacturer has issued a fix for this coderare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting load, engine speed and boost reading when the fault set. Check for related codes such as other pressure sensor, mass airflow or turbo control faults.
2. Visually inspect the sensor, its connector, wiring and any sensing hose for damage, chafing, oil contamination, corrosion or loose fit.
3. Inspect the whole charge air path, including hoses, clamps, intercooler and intake joints, for splits, oil residue and looseness. Pressure test it if the manufacturer's procedure allows.
4. With the engine off and ignition on, compare the live boost sensor reading with atmospheric pressure, and with other pressure sensor readings where fitted. It should read close to ambient.
5. Check the sensor supply voltage, earth and signal wiring against the manufacturer's specification, and test for voltage drop or resistance in the circuit.
6. Compare live boost against the target value during a safe road test or loaded test, and watch whether it tracks throttle and load smoothly or lags, spikes or sticks.
7. Test the turbo control actuator or solenoid and check wastegate or vane movement as per the model-specific procedure.
8. Check the air filter and look for exhaust restrictions if the real boost is out of line with the sensor reading.

How to fix

• Repair or replace leaking charge air hoses, clamps or the intercooler, and clean up any oil contamination in the system.
• Replace the boost pressure sensor if its readings are inaccurate or it fails testing, after confirming the wiring is sound.
• Repair damaged wiring or connectors, or clear and refit the sensing hose if it is blocked or split.
• Repair or replace the faulty turbo control actuator, solenoid or sticking wastegate or vane mechanism, following the manufacturer's procedure.
• Replace a blocked air filter and rectify any exhaust restriction found.
• Where the manufacturer lists an updated calibration for this fault, have the control unit updated after the mechanical and electrical causes are ruled out.

Can I keep driving?

Nearby codes

• P0235GenericTurbocharger/Supercharger Boost Sensor A Circuit
• P0237GenericTurbocharger/Supercharger Boost Sensor A Circuit Low