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Re: 528i & 540i radio wiring - Not the radio ! (archive)
[ Follow Ups ] [ 5-series (E39) Message Board ] [ Msg. Board FAQ ]
Posted by Jim Cash on October 05, 1999 at 09:20:40:

In Reply to: 528i & 540i radio wiring harness same? (Jim Cash) posted by TSB on October 04, 1999 at 22:20:39:

: I have a 528i Sport/5speed being built week 42 and the requested special order upgraded OBC (same as 540i) was denied by BMW AG. So here's my question: Is the wiring harness for the radio/OBC the same in both 528i & 540i, thereby allowing me to simply replace the stock radio/OBC with the 540i upgraded version?

: I've heard they are different. Can anyone (Jim Cash) confirm this and, if so, recommend an alternative solution to getting the upgraded computer?

: Tom B.

/i>
Tom - it has nothing to do with the radio. If you are "assuming" that the OBC is part of the radio because you see/control them from that panel in the centre of the dash then your assumption is wrong. That is the MID (multi information display unit and is nothing more than an I/O unit for those systems. Actually the radio is behind the tape panel and NOT physically part of the MID.

Now - to your question of upgrading the OBC. I think you are out of luck on this one. The OBC functions are actually part of the instrument cluster. The 528 has, what BMW refers to as, the "base cluster". The 540 has the "high cluster". There is a significant difference between them - not only from an info display aspect, but also from operation and interface to the rest of the car.

The High cluster in the 540 has aditional digital electronics and it is the controller for a second bus system (the instrument bus) which is not present on the cars with the base cluster. The I bus serves many other systems (radio, CD, tel, DSP, navigation CD, PDC, Lamp/Check control, etc.

It also is the interface to the diagnostic connector. All these things are served by the K (car) bus for the base cluster.

Soooooo - unless you want to put in a new instrument cluster and completely wire all these systems 9including software updates) I suggest you skip this OBC upgrade. Probably cheaper to buy a 540.


I am, however, confused as to why BMW AG would deny the order. From what I have seen the high cluster is available as an option on any model E39 in Europe. Maybe there is some current restriction in how they have programed the North American clusters - but that can be changed - I suspect that this must be the case and they did not want to make the change for one customer.

Cheers

Jim Cash



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