Motronic ECU error code

OK, new problem. Yesterday I had the car out for about 20 minutes of active driving for the first time since starting the major 7 months ago. I took the motor up to 6500 RPM and kept revs around 3000. The car performed well, no smokes, no leaks. It was idling a bit low at 5000 but smooth.
Today I vacuumed out the AC system, and while charging, after about 10-15 minutes the car stalled. With the AC on, the idle picked up to 1000, the vent temp came down to 60, the ac condensor and radiator fans came on as they should and all seemed well until it died. No fuel, no spark. I guess the ECU's did not like something?
Checked all fuses - OK
Unplugged and replugged all connectors on the relay board - NADA
I checked the Motronic diagnostic and I got the usual code for the "catalyzer" on the 7-12 bank, and then just rapid, steady short flashes with no pause. On the 1-6 bank I got the catalyzer code and then the RPM sensor code and then no more codes.
I unplugged and replugged the RPM sensors - no change.
I also noticed that the cabin AC fan was not working.
Any ideas on where to go next? I will check for 12 v on ECU pin 27 tomorrow.

 

Battery is a few years old but was fully charged before driving car two days ago. It still spins the motor rapidly.

 

OK, problem solved.
I was on the phone talking to Tim Fulmer and something clicked. The car stalled just after the radiator cooling fans kicked in. Also running were the ac condensor fans, the ac cabin blower and the fuel pumps. These are the exact circuits taken out of the fuse box in the Dave Helms conversion and all have a separate, common power lead from the battery. Tracing the power lead from the battery led me to an electrical junction block that I had installed. I very scientifically jiggled the wires and tried to start the car again and she roared to life (and NO CEL's) ! Upon closer inspection the set screw on one side of the junction was loose and I was able to pull both the red and white wires out with minimal tension. It was actually pretty lucky that this happened with the car in the garage rather than on a long cruise. Should I have tinned the ends of the large wires before putting them in the junction?
How would a real automotive electrical professional join all 3 wires together? A large crimp connector? I don't want this to ever happen again. I initially spliced in the junction to bring 12V to the white wire.
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You won't get any argument from me. In retrospect, I have no idea why I cut that wire in the first place. Maybe I will look into just running a new wire to the battery cable. I have to look at the other end and see how that mates to the Dave Helms conversion.

 

That makes sense, too flash. I have this three hole terminal block in my box of electrical components, but the set scerws will still tend to just push the wires to the side. Surely someone makes the correct junction for this type of application.

 

Another suggestion by Tim Fulmer would be to crimp two large ring terminals on the ends of the 8 gauge wire and then connect those via some junction block with studs and nuts (similar to the 512TR engine junction of the battery cable, alternator and starter wires. But where do you find such a thing? And remember it has to have a cover because the whole metal part is hot (12V).

 

I found this on Amazon last night. It should work perfectly with two ring terminals crimped onto the ends. I have a crimping tool for the job. Should I also solder the ring terminals to the wire? Would that hurt anything?
Amazon.com: Delphi/GM - Battery (+) 10mm x 1.5 Stud Covered Lid Battery Junction Box Distribution: Industrial & Scientific