01 Are All Hybrid Cars Automatic? The Truth About Hybrid Trans… • 02 This Is How to Fix a Car That Won’t Start After Replacing t… • 03 Adapting to Autonomous Transmissions: How Self-Shifting Car… • 04 Tesla Reveals The New Roadster And The First Thing Anyone N… • 05 Strangest Driving Laws Around the World • 06 How A Simple Mistake At The Gas Pump Could Destroy Your Eng… • 07 Serpentine Belt Noise: Causes, Effects, and How to Keep You… • 08 Mercedes-Benz unveils the eActros 600, a long-distance elec… • 09 Signs of a Failing Transmission Control Module (TCM) • 10 Automatic Transmission Brake Failure: Stop Your Car Without… •

DTC codes / P00xx · Fuel and air metering and auxiliary emission controls / P00C5

P00C5Turbocharger/Supercharger B Turbine Overspeed

P00C5 indicates that the engine control module has detected the turbine wheel of turbocharger or supercharger 'B' spinning faster than the manufacturer's safe limit, based on the speed sensor signal for that unit. The code is set when the calculated or measured turbine speed exceeds the overspeed threshold for a calibrated time, often triggering a protective power reduction.

SystemPowertrain
Code typeGeneric (all makes)
SeverityHigh
Fix difficultyProfessional
AreaFuel and air metering and auxiliary emission controls

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms
  • Reduced engine power or limp mode triggered by the ECM to protect the turbocharger
  • Audible whine or whistle from the turbocharger that rises in pitch with engine speed
  • Black smoke or excessive exhaust smoke under acceleration due to overboost or rich mixture
  • Loss of boost pressure or erratic boost gauge behavior if the ECM limits turbo operation
  • Possible transmission harshness or delayed shifts as torque management intervenes

Common causes, most likely first

  1. Faulty turbocharger speed sensor or damaged sensor wiring/connector
  2. Sticking or failed variable geometry turbo (VGT) actuator or vanes, causing uncontrolled overspeed
  3. Wastegate or bypass valve malfunction allowing excessive exhaust flow to the turbine
  4. Boost control solenoid or vacuum line leak causing overboost and turbine overspeed
  5. Restricted or leaking charge air cooler or intake piping altering boost dynamics
  6. ECM calibration issue or software glitch misreporting turbine speed
  7. Mechanical damage to the turbine wheel or bearing housing causing abnormal speed signals

How to diagnose and fix it

  1. Connect a scan tool and verify P00C5 is current, then check for related boost and sensor codes
  2. Inspect the turbocharger speed sensor and its wiring for damage, corrosion, or loose connections
  3. Check vacuum lines and boost control solenoid operation with a vacuum pump and gauge
  4. Test the wastegate or VGT actuator for free movement and correct calibration using a scan tool
  5. Perform a boost pressure test to identify leaks or restrictions in the charge air system
  6. Compare actual turbine speed data to manufacturer specifications under controlled conditions
  7. If all external checks pass, follow OEM diagnostic flow for internal turbocharger inspection or replacement

Overspeed codes often misdiagnosed as turbo failure

  • A sticking VGT actuator is a common cause of overspeed that many technicians overlook while replacing the turbocharger unnecessarily.
  • Boost control solenoid faults can command maximum boost, driving turbine speed beyond limits without any mechanical turbo damage.
  • The ECM may set P00C5 from a calculated speed model rather than a direct sensor, so a faulty sensor is not always the culprit.
  • After repairs, the ECM may require a relearn or adaptation reset for the turbo actuator to prevent repeat overspeed codes.
  • Exhaust system restrictions downstream of the turbo can alter pressure ratios and cause overspeed under load.

Can I keep driving with P00C5?

Driving with P00C5 is not recommended because continued overspeed can destroy the turbocharger and send debris into the engine. If you must move the vehicle, stay at low RPM and light throttle, and avoid any hard acceleration until the fault is repaired.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage