P0402 code meaning
EGR A Flow Excessive Detected
Powertrain system Generic code P04xx codes Check engine light
What P0402 means
Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx. P0402 means too much exhaust is recirculated, or exhaust flows although the valve should be closed – CARB explicitly requires a leaking valve to be detected. Ford's DPFE check at idle with EGR off expects no pressure difference above the engine-off value; Ford diesels compare the measured EGR rate with the expected one, GM diesels the fresh-air deviation in the opposite direction. Gasoline engines idle roughly or stall, diesels smoke and may lose power.
P0402 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium, DIY possible
- Typical labor1 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P0402
- Check engine light on
- Rough idle or stalling (gasoline)
- Jerking at part load
- Diesel: black smoke, loss of power
Common causes of P0402
- Most likelyEGR valve stuck open, dirt under the seat
- PossibleFord: DPFE sensor drifting or hose wrong
- PossibleDiesel: air leak between air mass meter and turbo, MAF drift
- Less likelyValve control opens unintentionally
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
EGR valveEGR valve seatDpfe sensorMAF sensor
What each part of P0402 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 4 | Area: auxiliary emission controls (catalytic converter, EGR, EVAP). |
| 02 | The exact fault in that area. |
What to do next
- Note P0402 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0402
What does P0402 mean?
P0402 means "EGR A Flow Excessive Detected". Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx. It is a generic code, so it means the same on every make.
Is it safe to drive with P0402?
Drive gently and only to a workshop. With P0402 the car can go into limp mode (reduced power) to protect itself.
Will P0402 fail an emissions test?
Yes, it can. P0402 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0402 to fix?
Difficulty: medium. A typical repair takes 1 to 3 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0402 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.