All codes
P0402Emissions System
EGR Excessive Flow Detected - Causes & Fixes
Diagnose the P0402 excessive EGR flow code, including stuck valves, blocked passages, and how to test the system.
What you may notice
Symptoms
- 01Check engine light on
- 02Rough idle or stalling at idle
- 03Hesitation on light acceleration
- 04Engine surging
- 05Failed emissions test
Where to look first
Common causes
- 01EGR valve stuck open or leaking
- 02Carbon buildup holding the valve open
- 03Faulty EGR position sensor
- 04Leaking EGR valve gasket
- 05Wiring or vacuum control fault
Step by step
What to check and repair
- 01Inspect and clean the EGR valve and passages
- 02Replace the EGR valve if it will not seat
- 03Check the EGR gasket for leaks
- 04Test the EGR position sensor and control circuit
- 05Verify vacuum or electronic control operation
What Does P0402 Mean?
The P0402 code indicates the ECM has detected more exhaust gas recirculation (EGR) flow than commanded. Too much recirculated exhaust dilutes the intake charge and can cause a rough or stalling engine.
Stuck-Open EGR Is the Classic Cause
A valve held open by carbon, or a leaking EGR gasket, lets exhaust flow into the intake when it should be closed. Idle quality is usually the first thing to suffer.
How AI4Car Helps
AI4Car lets you monitor EGR-related data and idle behavior, helping you confirm whether flow is excessive at idle when it should be zero.