What it means
Wastegate actuator B control voltage below expected range. Boost control tracks commanded vs. actual manifold pressure; persistent deviation means wastegate, vanes, hose or actuator are not delivering the requested pressure.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Wastegate actuator B controls boost by moving the wastegate or a related boost-control mechanism. The control module monitors the actuator B control signal and boost response, setting P0249 when the signal is below its expected range or boost does not follow the command; the code alone does not prove a mechanical actuator failure.
Common causes
Most likely first.
- Damaged wiring or connector
- Wastegate actuator B failure
- Poor electrical connection
- Control module fault
Symptoms
- Check engine light on
- Significant power loss / limp mode
- Possible blue or black smoke from exhaust
- Whistling or hissing sound from intake
How to diagnose it
- Capture freeze-frame data and compare commanded boost with measured boost and actuator B data if available.
- Inspect actuator B’s wiring, connector, and ground for damage, loose or corroded terminals, and poor contact.
- Test the actuator B circuit and actuator winding or electrical operation against the manufacturer’s specification.
- Inspect the actuator linkage, wastegate, and related hoses for binding, leaks, or disconnection that could disrupt boost response.
- If the circuit, actuator, and mechanical parts pass, follow the manufacturer’s procedure to assess the control-module output.
Common fixes
- Repair damaged wiring or poor connections in the actuator B control circuit.
- Reconnect or replace leaking or damaged hoses affecting the wastegate actuator B.
- Free or repair a binding wastegate or actuator linkage if inspection confirms it.
- Replace wastegate actuator B if it fails the specified electrical or functional test.
- Repair the control module only after confirming an output fault.
Can I keep driving?
Drive gently and avoid high boost, hard acceleration, and towing; the vehicle may lose power or enter limp mode. Stop if smoke is heavy, the intake noise becomes pronounced, or power loss makes driving unsafe.
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.