OBD2 codes.
A code identifies a signal or system that needs to be checked, not a part you should replace.
Got an OBD2 Bluetooth adapter? Read the codes straight from your car.1 code entry · 0 related faults
P0402The EGR valve is letting through more gas than expectedUrgency medium
Exhaust Gas Recirculation Flow Excessive Detected
The EGR valve sends part of the exhaust gas back into the intake to lower combustion temperature and reduce nitrogen oxides (NOx). This code means too much gas is flowing, or it flows when the EGR should be closed.
What the car has detected
With EGR switched off, the engine computer has measured recirculated gas flow above the calibrated value.
You can drive carefully, but if the valve sticks open the engine may run roughly, lose power or stall at idle. Get it checked soon.
Symptoms
- Engine warning light on
- Rough idle or stalling
- Lack of power
- Exhaust smoke on some diesels
Possible causes
- EGR valve stuck open, often from carbon
- Leaks in the EGR system
- Faulty valve wiring or connector
- Air leaks between the MAF sensor and the turbo, including the crankcase breather hose
- Faulty mass air flow sensor
Checks for the garage
- Check there are no other codes and that the air filter isn't clogged
- Look for leaks in the intake and vacuum lines
- Check the mass air flow sensor, which can also set the code
- Move the EGR valve with diagnostics (from almost closed to almost open) and see whether it responds and the air flow changes
- Check whether the valve and passages are blocked with carbon
Next step
Have the EGR valve checked for sticking open, and its wiring and intake leaks checked.
Go to a garage if the engine runs roughly or stalls, or if the code comes back. Checking the valve needs diagnostics.