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.

Real-world scan data

Seen in

2,309

scans in the past year

Found in

0.4%

of scans

0.7%

of scans that found faults

Appears alongside · share of P0402 scans

P0401in 55.5% of scans

P0704in 26.2% of scans

P0087in 23.5% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

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.

Read & clear P0402 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX