P0402 — Exhaust Gas Recirculation Flow Excessive
Moderate severityWhat it means
P0402 is stored when the engine control unit sees a fault involving the exhaust gas recirculation (EGR) system. The EGR system routes a little exhaust gas back into the intake to lower combustion temperature and NOx emissions. “Excessive flow” means too much exhaust gas is entering the intake, which can choke combustion at idle and low speed.
Common symptoms
- Rough idle, stalling or hesitation
- Pinging or knock under load
- Rough idle or stalling
- Failed emissions test
Likely causes
- EGR valve stuck open
- Leaking or stuck EGR control solenoid
- Carbon-clogged EGR valve or passages
- Faulty EGR valve, solenoid or position sensor
What to check first
- Check that the EGR valve closes fully and is not held open by carbon
- Remove and inspect the EGR valve and passages for carbon
- Command the valve with a scan tool and watch the engine response
Can you keep driving?
Often drivable, but pinging under load can damage the engine over time — avoid heavy loads until repaired.
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