P0402: Exhaust Gas Recirculation "A" Flow Excessive Detected
Too much exhaust is flowing back into the engine through the EGR system, often because the valve is stuck open.
What P0402 means
EGR is only supposed to flow at cruise and light load. At idle and wide open throttle, the valve should be closed. RepairPal explains that P0402 sets when the computer sees more EGR flow than it commanded, and lists excessive vacuum or electrical signal to the valve, a valve that opens too far or will not close, a failed vacuum solenoid and faulty feedback sensors as causes. Exhaust gas does not burn, so when too much of it enters the intake at idle, the engine runs rough, misfires or stalls. That is why RepairPal rates this code more urgent than insufficient flow codes and warns that ignition, fuel and oxygen sensor parts are often replaced by mistake. Carbon stuck under the valve seat is a frequent culprit. Shops check whether the valve is commanded open at idle, look at the feedback sensor, and pull the valve to inspect the seat. Replacing or cleaning the valve usually brings the idle back to normal.
Common symptoms
- Check engine light on
- Rough idle or stalling at stop signs
- Hesitation or misfire on acceleration
- Lack of power
- Poor fuel economy
Most common causes
- EGR valve stuck open or not seating
- Carbon holding the valve open
- Too much vacuum or electrical signal to the valve
- Failed EGR vacuum solenoid
- Faulty EGR feedback sensor
What to check yourself first
With the engine idling, check whether the EGR valve has vacuum when it should not; at idle most vacuum EGR valves should have none. A valve stuck open from carbon can sometimes be seen by removing it, but leave hot exhaust parts to a shop if unsure.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| Replace EGR valve | $489-$632 | If the valve is stuck open or leaking past its seat. |
| Replace EGR vacuum control solenoid | $129-$151 | When the solenoid lets vacuum through all the time. |
| Replace EGR valve position sensor | $107-$133 | If the sensor reports the valve open when it is closed. |
| Check engine light diagnosis at a shop | $125-$183 | RepairPal warns ignition, fuel and oxygen sensor parts are common misdiagnoses for this code. |
Typical US price ranges for parts and labor, not quotes. Your shop should confirm the cause with a diagnostic before replacing parts.
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Related codes
- P0401 Exhaust Gas Recirculation "A" Flow Insufficient Detected
- P0400 Exhaust Gas Recirculation "A" Flow
- P0404 Exhaust Gas Recirculation "A" Control Circuit Range/Performance
- P0108 Manifold Absolute Pressure/Barometric Pressure Circuit High
- P0300 Random/Multiple Cylinder Misfire Detected