Electrical and Computer Troubleshooting Help

This one is baffling me... but I feel I'm getting closer. I just need other opinions as to whether I'm on the right track (skip to #5 if you don't have time to read). My '98 540i has 185k miles on it.

Symptoms:

A] Air Bag Light came on

B] 2 days later, transmission stops shifting, no dash readout on gear position, no errors on dash.

C] Starter never engages on the first try. Will engage on second and subsequent tries only.

D] Voltage at idle too high (15.2v)

E] Battery charge a little on the low side (12.0v)

Actions Taken

1] Replaced alternator with new Bosch unit, system now charging at 14.7v - Good.

2] Battery replaced with new Bosch unit.

3] Ignition switch replaced.

Transmission still unresponsive, so took to dealer to reset codes. Dealer's computer can't connect to TCM, dealer thinks TCM/EGU needs replacement. Declined $1,350 dealer repair to self diagnose at home.

New actions taken:

4] Ordered used TCM/EGU from salvage yard. When installed, car won't start (starter never engages).

5] Went to Indy BMW repair shop. They could not communicate with old TCM/EGU, but could with the salvage yard unit. They used Autologic to reprogram salvage yard TCM but the car still would not start with that unit installed. HOWEVER, the dash indicator now reads gear position correctly. Indy tech thought VIN mis-match was preventing the car from starting. Put the original smoked TCM in car and it started right up, though stuck in 3rd gear.

6] Went home and researched how to reset VIN on salvage yard TCM. Finally reprogrammed TCM with correct VIN using WinKFP software and Gerts ADS Cable. But car still won't start.

So now I am thinking that either the odometer mis-match between the TCM and DME is preventing start or there is something wrong with the EWS at Electronic Immobilization Check that is preventing a start. Tried 2 different keys, still no start. Car will still start with old smoked TCM, but still stuck in 3rd gear if I use that one...

Any ideas people?

NEVERMIND... looks like I am screwed. EDIT - not true for EGS, see later posts where I succeeded!

I went into INPA and got this message in the ISN section of the EWS: "ERROR_ECU_REJECTED"

Hrm.... after some deep research on the ISN process, I have finally concluded that a used TCM/EGS can NEVER be reprogrammed to work with another vehicle manufactured after 3/97. Unfortunately that applies to me.

Page 22 of this EWS system PDF states that vehicles with an EWS III system do the following when any DME is changed:

"The DME will automatically burn the "Rolling Code Table" into its memory. Once the table has been burned into the DME memory it can NOT be changed. For this reason once a
DME is "Married" to the vehicle it will not work in any other vehicle."

Well, at least I learned a heck of a lot during this investigation. Time to pony up $1,200 for a brand new TCM. Sigh.

RPM Motorsports

Just had to replace my DME. Got one from a junk yard. Had it synced to my car by an independent shop. Worked great. Make sure the DME is the exact same one that you replace by Bosch part number or siemens not BMW part number.

Originally Posted by twitchit72

Just had to replace my DME. Got one from a junk yard. Had it synced to my car by an independent shop. Worked great. Make sure the DME is the exact same one that you replace by Bosch part number or siemens not BMW part number.

What year is your 3 series BMW?

Apparently the version of the EWS (car immobilization system) makes a difference as to how easy or difficult it is to replaces ECUs.

UPDATE - I decided to try a different salvage yard. HAH! It worked on the first try. So I can now confirm that a salvage unit EGS (TCM) works for a 1998 540i with the EWS III immobilization system. All you need to do is make sure it is the right Bosch number and program it either yourself using WinKFP or at the dealer using the program that was on the sticker (in bold numbers) attached to the original unit.. Just saved myself about a thousand bucks and learned loads. Thanks everyone.

Oh and BTW, RPM Motorsports in Canada was extremely helpful and kind. I highly recommend them to anyone experiencing ECU issues.