P00C5
Turbocharger/Supercharger B Turbine Overspeed.
- Generic
- Powertrain
- Generic code
- High severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 0
- AreaFuel and air metering, auxiliary emission controls
- C5
- FaultThe specific fault in that area
What it means
P00C5 means the engine control unit has detected that the turbine of turbocharger or supercharger 'B' (usually the second turbo on a twin-turbo or compound set-up, or the one on the second bank) is spinning faster than the permitted limit. The ECU sees this from a turbine speed sensor signal or from a calculated speed that is higher than expected for the commanded boost. Which unit is 'B' and how speed is measured depends on the model and engine.
Symptoms
- Engine warning light on
- Reduced power or limp mode
- Boost pressure higher than expected, or surging boost
- Whistling, siren or unusual turbo noise
- Hesitation or uneven power delivery under load
- Possible black or blue smoke from the exhaust
Possible causes
- Wastegate or variable vane mechanism sticking, seized or coked up, so boost cannot be releasedlikely
- Faulty boost control actuator, solenoid or vacuum/pressure supply to itlikely
- Turbine speed sensor fault, or damaged wiring or connector giving a false high readingpossible
- Exhaust restriction or boost control problem causing abnormal turbo loadingpossible
- Non-standard or outdated engine software calibration raising boost targets beyond turbo limitspossible
- Worn or damaged turbo (bearing wear, damaged wheel) giving erratic speed readingsrare
- Fault in the engine control unit itselfrare
How to diagnose
- Read all stored and pending codes and the freeze frame data, noting load, rpm and boost at the time of setting
- Check for related codes on boost pressure, actuator position, speed sensor and the other turbo, as they point to the root cause
- Inspect the turbine speed sensor wiring and connector, and the actuator wiring, for chafing, heat damage, corrosion or oil contamination
- Check the boost control hoses, pipes and solenoid for splits, leaks and blockages
- Command the actuator or solenoid with a scan tool and check it moves smoothly and fully, comparing commanded and actual values
- With the engine off, check the wastegate or vane linkage moves freely and is not seized or sooted
- Compare live boost and turbine speed against specification for your model, looking for overboost or spikes
- Inspect the turbo for shaft play, wheel damage and oil leaks, and check the exhaust for restriction, following the manufacturer procedure
How to fix
- Free or replace a sticking wastegate or variable vane mechanism, or the turbocharger if it cannot be repaired
- Replace a faulty boost control actuator or solenoid, and repair any leaking or blocked control hoses
- Repair damaged wiring or connectors, or replace a faulty turbine speed sensor
- Clear the cause of any exhaust restriction using the manufacturer repair procedure
- Where an outdated, faulty or non-standard calibration is the cause, have the correct approved software installed
- Replace the turbocharger if internal damage is found, and correct the cause of failure such as oil supply problems
Can I keep driving?
High severity
Avoid driving, or keep it to a minimum at light load, until it is diagnosed. Continued turbo overspeed can destroy the turbo and send debris into the engine.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.