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P0402 Exhaust Gas Recirculation (EGR) Flow Excessive Detected
What it means
The EGR system feeds a small amount of exhaust back into the engine to lower combustion temperatures and emissions. The computer detected more EGR flow than it commanded, usually because the EGR valve is stuck open or not closing fully.
Severity: Moderate
Can I drive it? Usually drivable, but too much exhaust gas at idle can cause rough idle, stalling, hesitation, and poor fuel economy. Fix it soon, especially if the engine stalls.
Common causes (most likely first)
- EGR valve stuck open from carbon buildup
- Faulty EGR valve or EGR position sensor
- Bad EGR vacuum solenoid or vacuum hose routing (older vehicles)
- Faulty DPFE or EGR pressure sensor (common on Ford)
- Wiring or connector problems in the EGR circuit
Likely fixes
- Remove and clean carbon from the EGR valve and passages
- Test the EGR valve and its sensor; replace if it won't close
- Check the EGR solenoid and vacuum hoses
- Replace the DPFE/EGR pressure sensor and its hoses on vehicles that use one
DIY parts cost
$30–$350
Approximate estimate
Shop repair cost
$150–$700
Approximate estimate, parts + labor
DIY difficulty
Moderate
Varies by vehicle
Cost ranges are rough, approximate U.S. estimates and vary widely by vehicle, region, and parts brand. Always confirm the diagnosis before buying parts.
Parts you may need
- EGR valveCheck price
- EGR valve gasketCheck price
- DPFE sensorCheck price
- Carbon cleanerCheck price
Affiliate links are placeholders. Verify fitment for your year/make/model.