P26C5: Exhaust Flow Control Valve A Control Circuit / Open

What it means

The controller cannot drive the exhaust flow control valve A (used for exhaust acoustics, EGR boost, or aftertreatment heating).

At a glance

• Usually lights the check-engine light

How it works

Exhaust flow control valve A is an electrically operated valve that can regulate exhaust routing or backpressure for functions such as exhaust sound, EGR flow, or aftertreatment heating. P26C5 sets when the controller detects an open control circuit and cannot drive valve A.

Common causes

Most likely first.

1. Open coil in valve solenoid
2. Broken control wire

Symptoms

• Check-engine light may be on
• Reduced engine power or altered response
• Exhaust or engine sound may change
• Emissions warning may appear

How to diagnose it

1. Scan for related exhaust or aftertreatment codes and review freeze-frame data for the conditions when valve A control failed.
2. Locate exhaust flow control valve A using vehicle service information and inspect its connector and harness for disconnection, heat damage, or broken wires.
3. Check the valve A solenoid winding for an open circuit using the manufacturer's test procedure and specification.
4. Check continuity through the control wiring between valve A and the controller, including connector terminals and any splices.
5. If the wiring and solenoid pass, verify the controller output using the manufacturer's diagnostic procedure.

Common fixes

• Reconnect or clean a loose valve A connector.
• Repair a broken wire or damaged terminal in the valve A control circuit.
• Replace valve A if its solenoid winding is open.
• Repair the controller circuit if its output is confirmed faulty.

Can I keep driving?

A short, cautious drive may be possible if the engine runs normally and no temperature or power warning appears, but avoid heavy loads until diagnosed. Loss of valve A control can alter exhaust flow, engine response, or aftertreatment operation.