What it means
The control module detects turbine speed above the permitted limit. It sets this code when the monitored turbocharger or supercharger turbine speed exceeds its calibrated threshold.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
- The engine or gearbox may go into limp mode
How it works
The turbocharger or supercharger turbine is the spinning part driven by exhaust gas or intake flow to provide boost. The module monitors turbine speed and sets P0049 when the monitored speed exceeds its calibrated limit. A boost-control or wastegate problem can allow excessive speed, while a turbocharger or supercharger fault can also contribute.
Common causes
Most likely first.
- Boost control or wastegate fault
- Turbocharger or supercharger fault
Symptoms
- Check engine light on
- Reduced engine performance
How to diagnose it
- Check freeze-frame data and live turbine-speed and boost readings, if available, to see how high speed related to engine load and commanded boost.
- Inspect boost-control hoses, wiring, actuator connections, and the wastegate mechanism for leaks, disconnection, or sticking.
- Compare commanded and measured boost and turbine-speed data using the manufacturer's diagnostic procedure.
- Inspect the turbocharger or supercharger for signs of damage or abnormal movement using the manufacturer's safe inspection method.
- Test the boost-control actuator and related sensors to determine whether a control fault is allowing turbine overspeed.
Common fixes
- Repair a leaking or disconnected boost-control line that is preventing proper regulation.
- Repair a sticking or failed wastegate or boost-control actuator after confirming the fault.
- Repair damaged wiring or replace a faulty boost or turbine-speed sensor if testing identifies it.
- Repair or replace the turbocharger or supercharger if inspection confirms mechanical failure.
Can I keep driving?
Avoid hard acceleration, high engine load, and towing because continued turbine overspeed can damage the turbocharger or supercharger and may lead to sudden power loss. If there is smoke, unusual whine or scraping, or a sharp loss of power, stop safely and arrange assistance.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.