E36 Cluster EEPROM/Coding Plug

[Artem]

Hey guys,

Just checking in really quick. A question for the experts...

My question is - does anyone know how all the information that is coded on the coding plug behind the cluster?

Situation is:
My gauge cluster is showing the wrong RPM, as per the norm when it comes to engine swaps.

I got several M3 gauge clusters with coding plugs, and I also have pigtails for the cluster, for testing things out or connecting to it.

My 318ti has the S52 motor from a 1999 convertible, its got the Motronic MS41.1 DME w. EWS delete.

My car has ~162k miles on it right now. One of the M3 clusters has ~78k miles, the other - ~138k. I want to maintain real mileage on whatever cluster ends up being installed in there.

I want to know if I can take my 318ti plug, put it in an E36 M3 cluster and 'align' it so that the mileage form my coding plug would be coded to the cluster - test mode 9, I believe.

However, I am afraid that if the coding plug contains engine information, the 318ti coding plug would thereby adjust the way the cluster interprets the RPM information from the DME and it will once again start being read incorrectly.

Does anyone know how the EEPROM for the coding plug store the information? Or if the aforementioned method would just make it work?

I originally wanted to use a microcontroller to alter the physical signal from the crownwheel, but once I knew how to make that solution work, I wanted to implement a more elegant solution by keeping it all OEM.

I have been through and through trying to get the damn PROGMAN/SSS/DIS to work to no avail - I got INPA and EDIABAS to connect and interact with the car via the FTDI OBDII adapter, but I couldnt get the rest of that virtual machine crap sorted out to the point of it working, and even when I got DIS to run, and saw all of the coding options, I didnt see any for the gauge cluster coding, so I figured, if I could just swap the coding plug and it would work, that would be ideal, or perhaps someone could think of another way of doing it, in which case, please do not hesitate to mention it here!

Thanks a ton!


GAUGE CLUSTER INFO (P.S.)
The coding plug behind the gauge cluster is an 8-pin EEPROM chip P/N 93C46. It communicating to the gauge cluster via UART or something along those lines.

The gauge cluster itself is very straightforward. Most of the bulbs switch on directly. The detailed explanation of all the features can be found here: http://www.bmwmotorsports.org/BMW_do...1driverino.pdf on pages 6-20

The parts you cant really find anywhere I found through interfacing the gauge cluster to a microcontroller - it is that the speedo and the tach are controlled by a 50% duty cycle square wave signal. The M3 cluster tach can receive the signal from 35-400Hz, which linearly represent about 600-8000RPM. Signals below 35Hz end up screwing with the gauge big time, and I havent tried much higher frequency signals, but that's the baseline.

The Speedo is also controlled by a similar 50% duty cycle square wave, but the frequencies end up being about 33-350Hz, which linearly represent 0-160MPH.