Engine and gearbox (P)
P0402: Excessive EGR Flow
The exhaust gas recirculation (EGR) system is allowing too much exhaust gas to flow back into the intake manifold. This can affect engine performance and emissions.
Checked by a licensed car technician · last reviewed 29 September 2026
Symptoms
- Rough idle
- Decreased fuel efficiency
- Increased emissions
- Engine hesitation
Common causes
- EGR valve stuck open
- Faulty EGR control solenoid
- Carbon build-up in EGR valve
- Vacuum leak in EGR system
How to check it yourself
- Check EGR valve closure at idle
- Inspect EGR valve for carbon build-up
- Test EGR control solenoid
- Check for vacuum leaks in EGR system
Can I keep driving?
The car can be driven, but prolonged driving with this issue can lead to increased emissions and potential engine damage.
General guidance, not a professional inspection. Confirm faults with measurements before buying parts, and use a qualified mechanic for brakes, steering, fuel leaks, airbags, and other safety-critical work. Terms and disclaimer