OBD-II · Engine and powertrain (P)
P0402
EGR flow excessive
What it means
More exhaust gas is being recirculated than the engine computer wants, often because the EGR valve is stuck open with soot.
Symptoms
- black smoke
- lack of power
- rough idle or stalling at idle
- engine warning light
Likely causes, most likely first
| No. | Cause |
|---|---|
| 01 | EGR valve stuck open by carbon |
| 02 | EGR control solenoid or actuator fault |
| 03 | vacuum hoses swapped or leaking |
| 04 | faulty EGR position sensor |
| 05 | air-mass meter fault |
What to check, step by step
- 01Check live data: EGR position at idle with EGR commanded closed, and air-mass reading.
- 02Use an actuator test to command EGR closed and compare valve feedback and air-mass response. If indicated, inspect whether the valve seats fully; disconnecting an electrical connector does not close a mechanically stuck valve.
- 03Remove, clean or replace the valve.
- 04Check vacuum routing and the control solenoid.
- 05Check the air-mass meter.