P23E7: EGR C Flow Insufficient Detected

What it means

Same as P049B 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 back into the intake, and its flow helps limit peak combustion temperature. The module detects less flow through loop C than expected, which can happen even when a valve moves if soot, a restriction, or a flow-control fault limits the exhaust path.

Common causes

Most likely first.

1. EGR passage or cooler C restricted by soot
2. EGR valve C not opening fully
3. Leak or restriction in the EGR path
4. Fault in EGR flow sensing or control

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 EGR C operation with available flow and position data to see when the shortfall occurs.
2. Inspect the EGR C valve connector and wiring for damage that could limit valve opening or distort flow feedback.
3. Check that valve C moves through its commanded range and inspect it for soot that restricts its opening.
4. Inspect the C-loop passage and cooler for soot buildup, blockage, leaks, or other restrictions.
5. Test the EGR C flow sensor or control components, if fitted, against the manufacturer's specification.

Common fixes

• Clean soot from the EGR C valve or restricted passage.
• Repair a leak or damaged connection in the C-loop flow path.
• Repair the valve C actuator or wiring if it does not open as commanded.
• Repair or replace a faulty EGR C flow-sensing or control component confirmed by testing.

Can I keep driving?

If the engine runs normally, cautious driving may be possible, but avoid heavy loads if power is reduced or the engine hesitates. Insufficient EGR C flow can raise NOx emissions and lead to an emissions test failure.