What it means
General electrical fault on the turbocharger boost control position sensor B — second position sensor on the same actuator (redundant Hall) or on a second turbo (twin-turbo, sequential or two-stage). With B invalid the ECM cannot cross-check actuator A and falls back to limited boost control.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Turbo boost control uses an actuator to position a wastegate or variable vanes, and position sensor B reports that actuator position to the engine control module. Sensor B may be a second feedback element on one actuator or the feedback sensor for a second turbo. This code indicates an electrical fault in sensor B's circuit, so the module may limit boost control if it cannot trust that feedback.
Common causes
Most likely first.
- Open or shorted wiring to the position sensor
- Failed Hall element
Symptoms
- Check-engine light on
- Reduced engine power or turbo boost
- Turbocharger control warning or limp mode may occur
How to diagnose it
- Record freeze-frame data and compare live readings for boost-control position sensors A and B to see whether B is missing, erratic, or implausible.
- Identify which actuator uses sensor B from the vehicle's wiring information, then inspect its connector and harness for heat damage, chafing, corrosion, or loose pins.
- Check the sensor's power, ground, and signal circuits for opens, shorts, or poor connections using the manufacturer's wiring diagram.
- With the circuit connected as specified, monitor sensor B while the actuator is commanded through its range and check for an interrupted or absent signal.
- If wiring and supplies are sound, test sensor B and the control module using the manufacturer's diagnostic procedure before replacing parts.
Common fixes
- Reconnect or clean a loose or corroded sensor B connector.
- Repair an open, shorted, or chafed sensor B wire.
- Replace a failed sensor B or actuator assembly if the sensor is not separately serviceable.
- Repair a confirmed faulty control-module driver.
Can I keep driving?
Avoid hard acceleration, towing, and high-load driving if power is reduced or boost control is erratic. The engine may limit boost or enter a protective mode, so arrange diagnosis soon and stop if the vehicle becomes unsafe to control.
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.