What it means
After start-up the boost-control loop on turbo A takes longer than the calibration limit to transition from open-loop to closed-loop control. Typically a slow-warming actuator (VGT vanes carbonised), a sluggish position sensor or a leaky pneumatic actuator that cannot follow setpoints quickly enough.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Turbocharger A's boost control system starts in open loop and then uses feedback to adjust boost as sensor readings become available. This code sets when the A-side control loop takes longer than its calibrated limit to enter closed loop, which can happen if carbon-restricted VGT vanes, a sluggish position signal, or a leaking pneumatic actuator responds too slowly.
Common causes
Most likely first.
- Carbonised VGT vanes
- Leaky pneumatic actuator
Symptoms
- Check-engine light may come on
- Reduced engine power or boost may occur
How to diagnose it
- Record freeze-frame data and note start-up conditions, then monitor commanded and actual turbo A position and boost data to see how long feedback takes to settle.
- Inspect turbo A's actuator hoses and connections for leaks, loose fittings, or damage if the system uses a pneumatic actuator.
- Check turbo A's position sensor connector and wiring for poor contact or damage that could delay usable feedback.
- Use a supported actuator test, if available, to check whether turbo A's actuator responds smoothly through its range.
- If feedback and actuator operation are sound, inspect the A-side VGT mechanism for sticking or carbon buildup using the manufacturer's procedure.
Common fixes
- Repair leaking or disconnected pneumatic actuator hoses on turbo A.
- Repair poor connections or wiring affecting turbo A position feedback.
- Service sticking or carbon-restricted turbo A vanes according to the manufacturer's procedure.
- Replace a confirmed sluggish actuator or position sensor.
Can I keep driving?
Short, gentle trips may be possible if the engine runs normally, but avoid towing and hard acceleration while turbo A control is slow to respond. Stop if power drops sharply, smoke increases, or the turbo makes an unusual noise.
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.