P0402
EGR A Flow Excessive Detected
Auxiliary emissions (EGR)
Generic OBD-II
Medium
What it means
P0402 means the ECM detects more exhaust-gas recirculation (EGR) flow than commanded — too much exhaust is being routed back into the intake. This usually makes the engine idle rough or stall, but it will still run. A valve stuck open with carbon, or a misreading EGR position sensor, are the common causes.
Medium
Can I keep driving? Usually driveable, but expect a rough or stalling idle — too much exhaust gas is entering the intake; it's fine short-term, though the rough running is worth fixing soon.
Common symptoms
What you'll notice
- Check-engine light on
- Rough idle, sometimes stalling at idle or low speed
- Hesitation or stumble under light load
- Slightly reduced fuel economy
Common causes
Most likely first
- EGR valve stuck or held open by carbon buildupLikely
- Faulty EGR solenoid or vacuum control letting the valve open too farCommon
- EGR position/DPFE sensor reading flow incorrectlyCommon
- Damaged EGR gasket or leaking passagesLess often
- Faulty ECM (rare)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data to see when the excessive flow is reported.
- Inspect and clean the EGR valve; check that it seats fully and isn't held open by carbon.
- Test the EGR solenoid and vacuum lines (if equipped).
- Check the EGR position or DPFE sensor against actual valve movement.
- Replace the valve or sensor if faulty, and clear the code. Re-test.
FAQ
Quick answers
Is it safe to drive with P0402?+
For a short time, yes, but excessive EGR can make the engine stall at idle and run rough. Fix it before the rough running strands you or worsens.
Can I just clear P0402?+
It returns if the valve is stuck open or the sensor is misreading. Cleaning a carboned-up EGR valve before clearing often solves it.
Related codes
Often seen with P0402
Read & clear P0402 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX