Here we see the importance of not being a parts fitter and actually testing what’s in front of you.
A BMW came to us for a diagnostic as it was going into limp mode. A full system scan found two codes for low oil pressure and another code for the swirl flap actuator long term drift.
Further investigation found the swirl flaps worked no problem at all. We then focused our attention on the low oil pressure and it was in fact very low, at nearly half of its nominal value it should be.
We then checked for technical service bulletins and found several for the wrong oil filter being fitted. We investigated and found the wrong filter had indeed been fitted; an inner central guide on the filter will locate the filter in the oil filter housing with the filter plug sealing up the filter housing drain hole.
If not filled correctly, the oil filter housing drain hole will not be sealed and will let oil escape back to the sump. We rang and spoke to the customer about our findings and he then mentioned he had only had a service done yesterday. If another garage had got their parts cannon out and let it rip at this vehicle, who knows what expense it could have been for such a simple mistake!