Full credit goes to p0lar for this writeup.
The E46 M3 is equipped with a sequence of 7 multi-function amber lights that tail the tachometer in a radial pattern from 4500 RPM to 7500 RPM. While the car is warming up, these lights are ordinarily used to indicate engine oil temperature; however, once the oil has reached the monitoring threshold, they become dormant, except on the SMG-equipped cars, where they become shift indicator lights.
The 'shift lights' feature on the E46 M3 was not enabled for manual-transmission cars from the factory, but was enabled for SMG-equipped cars by default. Though it's been explained elsewhere in great detail, this thread is simply the placeholder for the elements required to make the changes for 6MT-equipped cars, as well as a comprehensive list of the shift light location in all MSS54/MSS54HP DME variants.
As usual, the first step is to
identify the program version of DME. Once the DME's version has been identified, reference the following table and examine the byte at the proper offset.
You should see a string that looks as follows:
Alternately, you can also search the partial binary for 'C8 1E 06 00'.
----- BEHAVIOUR MODIFICATION -----
If you would like the shift light pattern to illuminate regardless of the sport mode setting, set the byte at the proper offset to '01' as follows:
If you would only like the shift light pattern to illuminate while in sport mode, set the byte to '02':
----- ERRATA -----
The shift light display will exhibit erratic behaviour when lowering the rev limits in neutral (either for "flat-foot shifting" or for 6MT "launch control" and may trigger on a shift regardless of in-gear RPM. There is no known workaround to date.