P00D8
Turbocharger/Supercharger Bypass Valve B Temperature Too High.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 0
- AreaFuel and air metering, auxiliary emission controls
- D8
- FaultThe specific fault in that area
What it means
P00D8 means the engine control unit has judged the temperature at turbocharger or supercharger bypass valve 'B' to be higher than expected. This is usually based on a temperature sensor reading, or on a modelled value on some designs, so the exact method depends on the vehicle. Which valve is 'B' (for example the second turbo or the second bank) also varies by model and engine, so check the manufacturer's information.
Symptoms
- Engine warning light on
- Reduced power or the engine going into limp mode
- Boost lower than normal or surging under load
- Whistling, fluttering or blow-off noises from the intake
- Hotter than normal intake air or poor fuel economy
- Possible additional boost or intake temperature codes stored
Possible causes
- Charge air cooling not working properly, such as a blocked or oily intercooler or a failed charge cooler pump or coolant circuitlikely
- Bypass valve sticking, leaking or not closing correctly, causing hot air to recirculatelikely
- Faulty temperature sensor or its wiring, connector or earth giving a false high readingpossible
- Boost leak or damaged intake hose forcing the turbo or supercharger to work harder and heat the airpossible
- Exhaust leak or missing heat shielding near the valve or sensorpossible
- Worn turbocharger or supercharger, or restricted air filter or intake, causing excess heatrare
- Outdated control unit software where the manufacturer has identified it as a known causerare
How to diagnose
- Read all stored codes and the freeze frame data, noting engine load, coolant temperature, intake temperature and vehicle speed when the fault set
- Inspect the sensor wiring and connector at the valve for heat damage, corrosion, chafing or poor pin tension
- Visually inspect intake pipes, clamps, intercooler and the bypass valve for splits, oil residue, loose joints and signs of leaks
- Compare the live valve temperature reading with other intake and coolant temperatures on a cold engine; a large unexplained difference points to the sensor or circuit
- Check the bypass valve moves freely and closes fully, using the manufacturer's method for that actuator (vacuum, electric or mechanical)
- Check the intercooler for blockage and, if fitted, the charge cooler coolant level, pump operation and flow
- Smoke test or pressure test the intake system for boost leaks
- Check the manufacturer's service information for software updates or technical bulletins covering this code on the specific model
How to fix
- Repair or replace the charge air cooler, or restore the charge cooler coolant level and pump function
- Clean, repair or replace the bypass valve or its actuator if it sticks or leaks
- Repair damaged wiring or connectors, or replace the temperature sensor if it reads incorrectly
- Repair intake leaks by replacing split hoses and refitting clamps
- Repair exhaust leaks and refit any missing heat shields
- Update the control unit software only if the manufacturer lists it as the fix for this code
Can I keep driving?
Short, gentle journeys are usually possible, but avoid heavy loads and hard acceleration because sustained high air temperatures can lead to reduced power and engine or turbo damage. Get it checked soon, and stop if the car loses power badly or you hear unusual noises.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.