What it means
The exhaust flow control valve B reports a control circuit low 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’s actuator controls exhaust routing for back-pressure or noise management. This code is set when the module detects an abnormally low condition on valve B’s control circuit, which can be caused by a wire shorted to ground, a shorted actuator coil, or poor connector contact.
Common causes
Most likely first.
- Control wire shorted to ground
- Internal short in actuator coil
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine light
- Reduced engine power
- Poor acceleration
How to diagnose it
- Check freeze-frame data and related codes to confirm the valve B control-circuit fault and the conditions when it occurred.
- Inspect valve B’s actuator connector and harness for corrosion, damaged terminals, or a control wire rubbed through to ground.
- Check the control wire for a short to ground and inspect the actuator power and ground paths using the wiring diagram.
- Measure actuator-coil and circuit behavior against the manufacturer’s specification to separate a wiring short from an internal coil fault.
- If the harness and connector pass, test valve B’s actuator and replace it if the coil is shorted.
Common fixes
- Clean and secure corroded or loose valve B actuator terminals.
- Repair the control wire if it is shorted to ground.
- Repair damaged wiring or connector pins.
- Replace valve B’s actuator if its coil is internally shorted.
Can I keep driving?
A short, gentle drive may be possible if the engine runs normally, but avoid hard acceleration because reduced power can occur. Stop if power loss makes the vehicle unsafe; valve B may not control exhaust routing correctly, affecting 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.