What it means
Position sensor B signal voltage below the lower limit — short to ground or open reference. 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
Turbo boost control uses an actuator to position a wastegate or variable vanes, and sensor B sends its position signal to the engine control module. This code sets when that signal falls below the circuit's expected lower limit, which can happen with a signal wire shorted to ground or a failed connection. The module may limit boost because it cannot trust sensor B's feedback.
Common causes
Most likely first.
- Signal wire shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Check-engine light on
- Reduced engine power or turbo boost
- Limp mode may occur
How to diagnose it
- Record freeze-frame data and compare live readings from position sensors A and B to confirm whether sensor B is stuck at a low value.
- Locate sensor B from the vehicle's wiring information and inspect its connector and harness for chafing, corrosion, water, or loose pins.
- Check the sensor B signal wire for a short to ground and inspect its reference, ground, and connector contacts using the manufacturer's wiring diagram.
- Move the harness gently while monitoring the signal to reveal an intermittent short or poor connection.
- If wiring and connections are sound, test sensor B and its supply circuits according to the manufacturer's procedure.
Common fixes
- Repair a signal wire shorted to ground.
- Clean or repair corroded or loose sensor B connector contacts.
- Replace damaged wiring or restore a faulty sensor reference or ground connection.
- Replace a confirmed faulty sensor B or actuator assembly if the sensor is not separately serviceable.
Can I keep driving?
Avoid hard acceleration, towing, and high-load driving if the engine has reduced power or boost. Sensor feedback may be unreliable, and the vehicle can enter a protective power limit.
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.