P23E8: EGR C Flow Excessive Detected

What it means

Same as P049C on EGR loop C. EGR mixes inert exhaust into intake to lower combustion peak temperature — too little raises NOx, too much causes misfires and rough running.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The EGR C stage routes exhaust into the intake to help control combustion temperature. The module detects more flow through loop C than expected, which can happen when valve C sticks open, fails to seal, or reports the wrong position.

Common causes

Most likely first.

1. EGR valve C sticking open
2. EGR valve seat not sealing due to deposits or damage
3. Fault in valve position feedback or actuator
4. Control wiring or module fault

Symptoms

• Check engine light
• Possible rough idle, hesitation, or reduced power
• Increased emissions or failed emissions test

How to diagnose it

1. Save freeze-frame data and compare commanded with reported EGR valve C position to identify when excess flow is detected.
2. Check for rough idle or hesitation and inspect the valve C connector and wiring for faults that could misreport its position.
3. Inspect the EGR C valve and seat for soot or damage that could keep the valve from sealing.
4. Check valve C movement and actuator response to determine whether it sticks open or does not follow commands.
5. If the valve and wiring appear sound, test its position feedback and control module output against the manufacturer's specification.

Common fixes

• Clean deposits from the EGR C valve and seat if they prevent sealing.
• Repair a poor valve C connector or damaged control wiring.
• Replace a worn or damaged EGR valve C that sticks open or will not seal.
• Repair the actuator, position-feedback circuit, or control module if tests confirm the fault.

Can I keep driving?

Avoid driving if the engine stalls, misfires, or runs very rough, particularly in traffic. Excess EGR C flow can worsen drivability and power and may increase emissions.