2001 BMW X5 ECM causing hard transmission down shift?

ONETROY

MEMBER
2001 BMW X5

I just bought a 2001 BMW X5, It runs and drives very well - The only problem I have is when stopping it downshifts hard (but Not all the time). I took it to a Transmission shop who scanned it and then they sent me to a second shop who scanned it- the 2nd shop said - I have 3 problems -1) ECM, 2) IAC or ISC and 3) MASS air flow sensor - They said the combination of these 3 is causing a premature down shift. Does this sound like it could be the problem? Or are they just trying to throw parts at the problem?

Thanks, Troy

1 Reply

DOCHAGERTY

MECHANIC
9,601 POSTS

As a BMW expert I can only advise within the parameters of the information provided in this forum. Cyberspace does not allow me the luxury to see the car and experience what the issue is, so I have to go with what you are telling me. The "ECM" as they refer to it, could be either the EGS (electronic gear selection) which is the "brain" for the transmission, or the DME (digital motor electronics) and the IAC is idle air control and the mass air flow meter. Having identified the components and giving them the correct names, the next step is to ask a few questions. Was or is the check engine light on? How long has this been happening? When does it seem to be present (engine cold or warm, going up or down hill, loaded or unloaded, etc.) How were the faults the shop you visited obtained? Exactly what were they? I usually like to know what the issue is before attempting to make any adjustments.