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Something very strange started happening with my 1999 E39 BMW 528IT:
- Occasionally the speedometer stops working (showing a speed of 0
mph), and of course this also messes up the MPG and MPH averages in the
on-board computer.
- When that happens, the automatic transmission also goes into FailSafe
mode (gear light goes on the cluster). With the car in "D", the
automatic transmission appears to be stuck into high gear, and is no
longer shifting up or down, making starts from a full stop very
sluggish. However I can still shift into 1st, 2nd or 3rd gear manually
if I want to, so I am guessing that the transmission is working fine,
and that the instrument cluster problems may have something to do with
this.
- The ASC and ABS lights are also on a lot (almost all the time),
although this could be caused by something else (or not...).

I took my car to the nearest BMW dealership, and they say that they
can't read the fault codes (diagnostic equipment cannot establish
connection with computer), so they are at a loss to tell me what is
wrong with my car...

Would it be possible for a faulty instrument cluster to cause such
problems?

I don't think the transmission is bad, as I can shift manually - I
suspect that this might an electrical problem of some sort, but without
diagnostic codes, it's hard to tell what to replace before finding the
root cause to the problem...

Thanks,

JP Abello

[Jeff Strickland]

You only mentioned that the speedo stops working. This can be caused by the
Speed sensor in the differential. (Its in the diff in my car, a '94 3
Series, it could also be located on the output of the transmission.) This
can cause the car to go into Limp Mode because the car needs speed
information as part of what it uses to decide what to do next.

I don't think the trans is faulty either, I think it's responding to the
lack of needed information.