What it means
The exhaust flow control valve A responds to commands but the resulting flow or back-pressure does not match expectations. Worn flap or carbon coking on the bore.
At a glance
- Usually lights the check-engine light
How it works
Exhaust flow control valve A changes exhaust flow or back-pressure as commanded by the control module. This code sets when the valve responds but the resulting flow or pressure does not match expectations, which can happen if its flap no longer seals or carbon buildup restricts its travel.
Common causes
Most likely first.
- Worn valve flap loses sealing
- Carbon coking restricts valve travel
Symptoms
- Check-engine light may be on
- Reduced engine performance or altered exhaust response may occur
- Exhaust or turbocharger-related warning may appear, depending on the vehicle
How to diagnose it
- Record freeze-frame data and review live data for valve A command, position, and any available exhaust pressure readings when the fault occurs.
- Inspect valve A's wiring, connector, and external linkage for damage, looseness, or binding.
- With the exhaust cool, check the valve and bore for carbon deposits or visible flap wear that could restrict movement or prevent sealing.
- Use the manufacturer's scan-tool procedure to command valve A through its range and compare the response with the reported position.
- If movement appears normal but flow remains out of range, test the related pressure or flow readings using the manufacturer's diagnostic procedure.
Common fixes
- Clean carbon buildup restricting exhaust valve A, if the valve is serviceable.
- Repair a binding linkage or damaged connection at valve A.
- Replace valve A if its flap is worn or no longer seals correctly.
Can I keep driving?
If the engine runs normally and no temperature or exhaust warning appears, limited driving may be possible; avoid towing or heavy acceleration if power is reduced. Stop if performance deteriorates sharply or a warning indicates an exhaust or turbocharger problem, since incorrect back-pressure can affect engine operation.
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.