Parts
$40–180
P0402 — Exhaust Gas Recirculation Flow Excessive
SAFEIs it safe to drive? Emissions-related fault that won't leave you stranded — drive normally but get it diagnosed before your next inspection.
What P0402 means
The EGR system recirculates a metered amount of exhaust gas back into the intake to lower combustion temperatures and reduce NOx emissions. 'Excessive flow' means too much EGR is getting in — often a valve stuck open or a position sensor reading incorrectly.
Most likely causes (in order)
- EGR valve stuck open (carbon buildup holding it open — clean or replace)
- EGR position sensor faulty (tells ECM valve is closed when it's open)
- EGR passages clogged with carbon causing pressure differential issues
- DPFE sensor (Ford) failed or hoses swapped/cracked
- Vacuum line leak allowing EGR to open unintentionally
Symptoms you might notice
- rough idle
- stumble at low speed
- hesitation on tip-in
- occasional stall
What to check first
Disconnect the EGR vacuum line (or command the valve closed on a scan tool) and see if idle quality improves immediately — if it smooths out, the valve is stuck open or leaking through.
Repair cost & difficulty
Labor
0.5–2 hr
Difficulty
DIY-friendly