My last post about the M3 covered removal of the rear subframe. With the subframe out, the last of the wiring harness could be fished out of the car. I had previously disconnect all the electrical components, leaving the main chassis harness in the car. I wanted to maintain as much integrity to the harness as possible, so no easy snipping of wires here. Well… I did cheat and cut the harnesses running to the doors and trunk lid, as both would be gutted and no need to save the wiring.
The entire harness runs to a single hole in the firewall, where it enters the relay/fuse box found beside the brake booster, behind the left front strut tower. This box is secured to the firewall with a few nuts, which are accessible from the driver’s footwell. With the box loose from the firewall, I was able to feed the harness out of the interior of the car.
Now the real work: laying the whole harness out in order to determine what needs to be saved to rewire the car for race car minimums.
at 18:53
Is there anyway possible you remember what you cut out of the chassis harness? I have a 98 M3 and I believe I might have cut out too much from mine.
at 19:09
Sorry, on that car I completely stripped all the wiring. It was going to be a completely custom harness.
at 20:02
What did you base your custom harness off of?
I’ve spent hours upon hours staring at wiring diagrams for my OBDII M3. I had my DME tuned and am experiencing a no-crank issue. I’m thinking about just scrapping the remaining chassis harness and making a custom one as you did but I’m not entirely sure how to get started.
at 20:06
I actually never finished that car, scrapped it due to some frame damage. I was planning on using a power distribution module, something like the MoTeC line. Of course this was on an OBDI with EWS deleted. Have you checked that all your EWS components are still wired? Have you connected any type of diagnostics?
at 20:18
I had my EWS completely removed from the mapping of my DME. I’m currently try troubleshooting the issues I’m having with the performance group that tuned my DME. I’m not entirely sure if I might have cut something out of the chassis harness that I shouldn’t have. I removed cruise control, AC, heater core, all radio wiring, cigarette lighter, info module. Pretty much everything from the dash that didn’t prevent the car from running.