What it means
The exhaust flow control valve B reports a position circuit range/performance condition. Exhaust routing for back-pressure or noise control cannot be commanded reliably.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
- The engine or gearbox may go into limp mode
How it works
Exhaust flow control valve B changes exhaust routing for back-pressure or noise management, while its position sensor lets the module compare actual movement with the requested position. This code means valve B’s position signal is outside the expected range or does not follow the commanded movement, which can result from sensor drift or loose linkage.
Common causes
Most likely first.
- Sensor offset drifted
- Linkage between sensor and valve loose
- Sensor element aged beyond calibration window
Symptoms
- Check-engine light
- Reduced engine power
- Poor acceleration
How to diagnose it
- Review freeze-frame data and compare valve B’s commanded and reported positions with a scan tool to find when they diverge.
- With the exhaust cool, inspect valve B’s sensor-to-valve linkage for looseness, slipping, binding, or damage.
- Check the position sensor mounting, connector, and wiring for movement or poor contact that could distort the reading.
- Use an available actuator command to watch valve B travel and see whether the position signal tracks smoothly.
- Test sensor output and linkage movement against the manufacturer’s specification to distinguish sensor drift from mechanical play.
Common fixes
- Secure or adjust loose valve B sensor linkage.
- Repair damaged wiring or a poor sensor connection.
- Replace valve B’s position sensor if its output is outside the manufacturer’s calibration range.
- Repair or replace binding or worn valve B linkage.
Can I keep driving?
If power remains normal and the engine runs smoothly, limit driving to a short trip for diagnosis. Avoid hard acceleration because reduced power may occur, and a valve that does not follow commands can impair drivability and emissions.
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.