What it means
The exhaust flow control valve C reports a control circuit low condition. Exhaust routing for back-pressure or noise control on this branch 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 C uses a control circuit to change exhaust routing on its branch. The engine control module detects an abnormally low circuit signal, which can result from a short to ground, an internally shorted actuator, 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
- Change in exhaust sound
- Reduced engine performance
How to diagnose it
- Read freeze-frame data and valve C command and circuit data to establish when the low signal was detected.
- With the exhaust cool and the system powered down as specified by the manufacturer, inspect valve C’s harness and connector for chafing, corrosion, moisture, or pin damage.
- Check the control wire for a short to ground and compare circuit measurements with the manufacturer’s specifications.
- Inspect valve C’s connector terminals for corrosion or high-resistance contact, and verify the connection under the manufacturer’s test procedure.
- If wiring and connections are sound, test the actuator coil and control-module output for a short or other fault.
Common fixes
- Clean and secure corroded or poorly seated valve C connector terminals.
- Repair a valve C control wire that is shorted to ground or damaged.
- Replace valve C’s actuator if its coil is internally shorted.
- Repair a confirmed control-module circuit fault if the harness and actuator test correctly.
Can I keep driving?
If the vehicle remains stable, drive gently and avoid hard acceleration; stop if engine performance drops sharply or the exhaust becomes unusually loud. A low circuit signal can prevent valve C from controlling exhaust routing reliably, so arrange prompt diagnosis.
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.