P0249

What it means

P0249 means the engine control unit has detected a low signal or low circuit state on the control for wastegate actuator 'B'. This is usually the second wastegate on a twin-turbo or compound set-up, but which actuator is 'B' depends on the model and engine. The unit saw the control circuit voltage or feedback sit below the expected range, so it cannot control boost on that side correctly.

Symptoms

• Engine warning light on
• Loss of power or reduced boost, often with the engine in limp mode
• Uneven or inconsistent boost between turbochargers on twin-turbo engines
• Overboost or underboost, depending on the position the wastegate fails in
• Poor acceleration or hesitation under load
• Whistling or fluttering from the turbo area

Possible causes

• Wiring fault in the wastegate actuator control circuit, such as a short to ground, chafed insulation or a damaged connectorlikely
• Faulty electric wastegate actuator or control solenoid B (internal short or failed motor or position sensor)likely
• Corroded or loose connector terminals, or water ingress at the actuator plugpossible
• Wastegate linkage seized or sticking from carbon build-up or heat damage, overloading the actuatorpossible
• Low or unstable supply voltage or poor earth to the actuator or control unitpossible
• Engine control unit driver fault or outdated calibration, where a known fault exists for that modelrare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting load, rpm and battery voltage when the fault set, and check for other boost or turbo codes.
2. Look over the wastegate actuator, its wiring and connector for heat damage, chafing, corrosion, moisture or loose pins.
3. Check battery condition and charging voltage, then check the relevant fuses and earth connections.
4. With a scan tool, command the wastegate actuator B and compare the commanded and actual position or duty cycle.
5. Check the supply, earth and signal wires at the actuator connector against the manufacturer's wiring diagram, including continuity and shorts to ground.
6. Move the wastegate linkage by hand, with the engine off and cold, to check for sticking or excessive play. Follow model-specific procedures for electric actuators.
7. Check the actuator's resistance or response against the manufacturer's specification, as the method depends on whether it is electric or vacuum-controlled.
8. Check for any technical service bulletins or calibration updates for your model before replacing the control unit.

How to fix

• Repair or replace damaged wiring and clean or replace faulty connector terminals.
• Replace the wastegate actuator or control solenoid B if it fails electrical or functional tests, and perform any required adaptation or calibration procedure.
• Free or replace a seized wastegate linkage, or the turbocharger if the wastegate assembly cannot be repaired separately.
• Repair poor earths or supply voltage faults and fix any battery or charging problems.
• Update the control unit software only if the manufacturer lists an outdated calibration as a known cause, or repair or replace the unit if it is proven faulty.
• Clear the codes and road test to confirm that boost is correct and the fault does not return.

Can I keep driving?

Nearby codes

• P0248GenericTurbocharger/Supercharger Wastegate Actuator B Range/Performance
• P024AGenericCharge Air Cooler Bypass Control A Range/Performance