Update:
Okay, my electrical engineer dad came over today and we did a bunch of sleuthing. Here's what we did/found:
- We opened up my old DME and measured continuity on all the pins in the most corroded-looking connector. They all are getting good contact.
- We cleaned [the living f**k] out of that connector with plastic-safe contact cleaner and popped each of the little sub-connectors on and off the old DME pins to clean them the best we could.
- The battery was low after sitting, about 12.1V and then 11.9V after turning the key. We used the reliable old Denali to jump first at the battery in the trunk. This resulted in a big voltage drop for some reason. It could just be that we weren't able to get a reliable connection on the battery. However, with the truck battery showing 12.9V, we were only able to see 12.5V at the X5 battery post.
- We jumped from the under-hood battery posts and we were able to get 14V from the Denali and read with the voltmeter at the BMW battery. The assumption is still that the connection on the jumper cables was bad in the trunk, but just recording our notes for posterity.
- We checked every single fuse again with the voltmeter to make sure we weren't seeing any voltage across them. All fuses appear to be good.
- I triple checked that the immobilizer was installed correctly.
- With 14V being pumped in, we tried to start the car again. No start. The DME still doesn't show up on the Foxwell. However, we got a new warning on the dash: "TRANS: FAILSAFE PROG" and "ENGINE FAILSAFE PROG".
- Went into the Foxwell and saw that there was a new extra code in the transfer case module stating that it had enabled limp home mode. I cleared it. Still no start.
- We unplugged the immobilizer and ran another quick scan on the Foxwell. It does the same thing as the DME-- it just doesn't show up. No fault, just no immobilizer module on the list.
So, my BMW is still "doing BMW things" and holding down the concrete in my driveway. This thing is making me crazy. Any ideas? Our next logical step is to clean out ALL the connectors and check them all for continuity, one wire at a time.
If that doesn't work, I'm going to try and send my DME, my VVT, my immobilizer, and my key back to ECU Pro and see if they can just confirm it all still starts their test vehicle.
If THAT still isn't fruitful, I guess I need to start looking at a professional shop to really deep-dive into this wiring issue, assuming that's what it is. Seriously, anybody want this thing?? Kidding... but not really kidding.
Missing carburetors and points...