P0402: Exhaust gas recirculation (EGR) flow excessive
More gas is flowing through the EGR than it should, often because carbon holds the valve open. It causes a rough idle and hesitation.
| Code | P0402 |
|---|---|
| System | Engine and transmission |
| Group | P04xx, Emissions control |
| Type | Generic: it means the same on every make |
| Can you keep driving? | With care |
What P0402 means
The ECU detects exhaust gas entering the intake when the EGR should be closed or nearly closed. Too much recirculated gas smothers combustion, especially at idle and low revs.
Most common causes
- EGR valve stuck open with carbon
- Misrouted vacuum hose holding it open (vacuum operated valves)
- Vacuum solenoid that does not shut off
- EGR position sensor reading incorrectly
- Faulty EGR valve
Symptoms
- Rough idle or engine stalling
- Hesitation and lack of power at low revs
- Hard starting
- Engine warning light on
Can you drive with P0402?
With care You can drive carefully, but the engine may stall when you stop at a junction. Take it to a garage soon.
Open the bonnetthe in-depth explanation
How to check it
With the engine idling, check EGR position on your reader: it should be closed. If it stays open, or idle improves when the valve is unplugged, tell the garage.
How to read and clear P0402 with Final OBD
Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P0402 with its description and whether it’s confirmed, pending or permanent.
If the engine stores it over standard OBD, with FREE you read this code with its explanation for nothing and clear it. With PRO you also read the faults of every control unit and clear them in all of them.
Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before an inspection. It’s all in how to read and clear fault codes and in inspections and OBD.
Similar codes
- P0400 Exhaust gas recirculation (EGR) flow malfunction
- P0401 Exhaust gas recirculation (EGR) flow insufficient
- P0403 EGR control circuit malfunction
- P0404 EGR circuit range or performance problem
- P0405 EGR sensor A circuit low
- P0406 EGR sensor A circuit high
- P0407 EGR sensor B circuit low
- P0408 EGR sensor B circuit high
- P0409 EGR sensor A circuit malfunction
- P0410 Secondary air injection system malfunction
To understand it properly
We explain how that system works, with drawings and no waffle, in our mechanics guide: EGR and particulate filter.
What does code P0402 mean?
The ECU detects exhaust gas entering the intake when the EGR should be closed or nearly closed. Too much recirculated gas smothers combustion, especially at idle and low revs.
Can you drive with P0402?
You can drive carefully, but the engine may stall when you stop at a junction. Take it to a garage soon.
How do you clear P0402?
With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, P0402 comes back.
Read it on your car
Final OBD reads and clears engine faults through standard OBD for free, each one explained in plain English. With PRO it also reads the faults of every control unit, each make’s own codes included, and clears them in all of them.
