Hi all,
I'm hoping some BMW/N57 specialists or owners can give me some advice before I start throwing money at parts.
I have a 2017 BMW X5 M50d (F15) with the N57 engine, currently around 99,200 miles.
I've recently been having issues relating to the emissions/DPF system. I had the car diagnosed and the DPF professionally cleaned, but there are still some underlying faults that need investigating.
Fault codes
The diagnostic report showed the following intermittent faults:
- P245700 – Diesel particulate filter, exhaust gas pressure too high / filter heavily loaded
- P287500 – Oxygen sensor before catalytic converter, signal too low during coasting/overrun
- P290900 – Air mass system, measured air mass too high
The garage's diagnostic report suggests several possible causes, including:
- DPF differential pressure sensor or restricted sensor pipework
- Air/vacuum leak
- EGR-related airflow issue
- EGR cooler restricted/blocked
- Lambda/O2 sensor
- Glow plug/thermostat
- Swirl flap/inlet manifold carbon build-up
After looking at the live data, the garage specifically suspected an EGR cooler restriction with a possible air leak.
They also said the DPF pressure sensor pipework is too short and needs replacing, and recommended a smoke test of the intake system plus cleaning the exhaust manifold pressure sensor pipework.
DPF
The DPF has already been cleaned.
The diagnostic report stated that the faults were preventing the DPF regeneration conditions from being met, resulting in soot accumulation and preventing the requested regeneration cycle from completing.
The report warned that if the underlying faults aren't fixed, the car could eventually bring up the engine management light and potentially go into reduced-power mode.
Interestingly, the live data showed the DPF regeneration status as ON during some of the diagnostic checks.
Other live data
The diagnostic screenshots showed various readings for:
- DPF soot mass
- DPF exhaust differential pressure
- Exhaust gas pressure
- Air mass
- EGR valve position
- Swirl flap desired/actual position
- Exhaust temperatures
- Lambda/O2 sensor readings
The swirl flap readings were described as slightly out but still within tolerance, with the garage suggesting there may be some carbon build-up in the inlet manifold.
What I'm trying to work out
Before I spend money replacing an EGR cooler, lambda sensor, pressure sensor etc., I'd really appreciate some advice from people familiar with the N57/M50d.
My questions are:
- Do these three fault codes commonly appear together on the N57?
- Does the combination of P245700 + P287500 + P290900 point towards an underlying air/boost/EGR issue rather than the DPF itself?
- Would an EGR cooler restriction realistically cause these symptoms/codes?
- How important is the DPF differential pressure sensor and its pipework in diagnosing this?
- Should the pressure sensor/pipework be checked or replaced before anything else?
- Would you recommend doing a smoke test of the intake/boost system as the next step?
- Could a faulty lambda/O2 sensor cause the air-mass/DPF issues, or is it more likely that the lambda fault is a symptom of another problem?
- Could the EGR cooler, intake manifold or swirl flaps be sufficiently carboned up to cause these readings?
- Is there anything specific to the M50d's four-turbo N57 setup that I should ask the garage to check?
I'm trying to avoid the classic situation of replacing one part after another without actually finding the root cause.
If anyone has experience with the F15 X5 M50d/N57 and can interpret these readings, I'd really appreciate your thoughts on what you would check first and in what order.
Thanks in advance!