Applies to: BMW and MINI models with the 1.5-litre B37 and 2.0-litre B47 diesel engines – including F55 and F56 Cooper D models and equivalent BMW 1 Series, 2 Series, and X models with the same engines.
The Diesel Engine Fault BMW Doesn’t Want to Talk About
If you drive a 3rd Gen MINI Cooper D or a BMW with the 1.5d (B37) or 2.0d (B47) engine, this fault could cost you thousands — or relatively little if caught early.
On early models (pre 2019), the fuel pressure sensor can leak diesel into the wiring loom. Because diesel is an oil, it wicks its way through the loom, spreading through the connectors — and in severe cases, all the way into the ECU itself.
What We Found
- Fuel pressure sensor leaking throught the sensor itself, into the loom
- Diesel contamination tracking down multiple branches of wiring
- In this case: diesel inside the ECU casing
What BMW Would Do (costing £2k+)
- Replace the fule pressure sensor
- Replace the engine loom
- Replace everything that the loom connects to
- Replace the ECU itself
What We Did
- Replaced the fuel pressure sensor
- Replaced the engine loom
- Cleaned every plug that the contaminated loom connects
- Cleaned and repaired the ECU internally — no need for dealer replacement
Most main dealers would condemn the ECU outright. We carefully opened it, cleaned the board with solvent, dried it thoroughly, and resealed it — saving the customer thousands.
FAQs
Which engines are affected?
This fault has been seen on 1.5d (B37) and 2.0d (B47) diesel engines in both MINI and BMW models, mostly from 2014–2020.
What are the symptoms?
Common symptoms include a diesel smell, electrical issues, warning lights, misfires, or ECU communication faults. Sometimes you’ll find diesel pooled around the pressure sensor connector.
How far can the diesel spread?
We’ve seen it wick through multiple wiring branches and reach the ECU itself. Left too long, it can corrode connectors and short internal electronics.
Can the ECU be saved?
Yes, in many cases. If it hasn’t been damaged beyond repair, we can open it, clean the internal board, and reseal it properly. This avoids a very expensive dealer-supplied ECU replacement.
Is this a known issue?
It’s not widely publicised, but we’ve seen enough examples now to know it’s a real design weakness. Catching it early can prevent major damage.