That I do not unfortunately. I don’t work on enough of them to justify the cost of the tool, and even the ones I typically dig into are E36’s where most of the diag doesn’t require one. I do have a bosch hammer from when I used to service P-cars alot for PCA, but my programming is only for Porsche 964, 993, and GT3’s/Turbo’s. At $2800 even that was a stretch for me .
Second paragraph speaks natures of a faulty ground. Alternator frequency backfeeding through the harness because it found a better path than the one it should be taking. BMW loves to stash a few of the common ground points way under the dash, and up on the firewall. I’d even just check the neg batt cable and/or the main engine ground strap. Typical german car crap in reality.
The cluster thing is another issue. BMW clusters are a friken mini computer themselves and have a mind of their own. Don’t know much about them myself, other than just replacing with a known good unit first for testing before digging through harnesses for diag.
I would certainly test the DME, or if possible swap out with another car(will possibly require key transponder coding in the DME, never swapped e46 DME’s before.)
I’ve been ripping through the S54 diagrams to attempt a twin DME setup for the kit car V12 in the event one does sell. Same thing Porsche used to do on the 956/962 with the Motronic and basically turned a flat six motor into two three cylinder engines mated at the crank. Every sensor doubled up. Not many other options for running quad C.V. VANOS other than that, Motec M800, or OBR! I have an entire E46 M3 harness here and it’s by far the knarliest electrical mess I’ve encountered. I haven’t even begun to cut it open yet. Looks like it’s gonna be a blast. I’ll take note of those wire coding mistakes though, thanks for the heads up on that 