EGR flow excessive on BMW diesel — N47/N57 stuck-open valve, often preceded by the well-known EGR cooler recall.
BMW P0402 — EGR flow excessive on BMW diesel — N47/N57 stuck-open valve, often preceded by the well-known EGR cooler recall. Typical UK independent garage cost: £350–£1200.
What actually causes P0402 on a BMW
N47/N57: BMW ran a global EGR cooler recall due to fire risk (cracked coolers vent hot exhaust into the airbox). Post-recall coolers are better but the valve still carbons up. Symptom of a stuck-open valve is P0402 plus rough idle when hot.
BMW engines that log P0402
- N47 2.0d (F30 320d, E90 320d)
- N57 3.0d (F10 530d, F30 335d)
- M47 2.0d (older 320d)
How we diagnose P0402 on a BMW
- VIN check for EGR cooler recall (Bimmerfest/dealer)
- ISTA live data — EGR commanded vs actual, MAF vs expected
- Remove EGR and swirl flap assembly, deep-clean
- Fit OE Pierburg valve; renew cooler if recall completed
The common misdiagnosis to avoid
Not checking the recall status — BMW will replace the EGR cooler free on eligible VINs. Also, don't clean the N47 EGR in situ; the intake manifold swirl flaps must come off to do it properly.
BMW P0402 repair cost in the UK
Expect £350–£1200 including parts and labour at an independent garage. Main-dealer quotes on BMW are usually higher for the same job, and the spread exists because the cheap cause and the expensive cause throw the same code — pay for the diagnosis before you pay for parts.
Bob's workshop tip
BMW N47 320d — check the EGR cooler recall FIRST. Free parts if eligible.
Codes usually seen alongside P0402 on BMW
- P0401
- P0403
- P244A
Symptoms drivers report with P0402
- Rough idle, often shaking the gear lever
- Hesitation off the line
- Stalling at junctions
- Possible black smoke at idle
- Engine warning light + power reduction warning
Repairs that clear P0402
- EGR clean or replace
- Sensor inspection
For the generic, all-makes explanation of this code — meaning, every known cause and UK cost bands — see our P0402 guide.
Reading P0402 on a BMW properly
A generic reader will show P0402 and nothing else. What matters is the freeze-frame data stored with it — engine speed, load, coolant temperature and fuel trims at the moment the fault was logged — plus whether any other module on the BMW has logged something at the same time. Codes rarely arrive alone, and the order they were stored in usually points at which one is the cause and which are the consequences.
Clearing P0402 without fixing it
Erasing the code resets the BMW's readiness monitors as well as the light. The fault returns on the next drive cycle if the cause is still there, and in the meantime the incomplete monitors can stop the car passing an emissions check. After a genuine repair, the car is driven until the relevant monitor completes before it is handed back.
Bob's Mechanical Repairs is an independent garage in Birnam, Dunkeld, Perthshire, with 32 years of Bob's experience on the tools. If P0402 is showing on your BMW, bring any scan results with you — we will read the live data ourselves, confirm which cause it actually is, and price the repair before any work starts.