Stalling with brake application and reverse light stays on and...

My 96 900SE just started having this issue after 2 weeks of driving. It only has 110,000 miles on it but I think it may have sat for about a year in NH where I got it.
Anyway, just yesterday the brake light failure message popped up on the SID in the morning while I was driving. I stopped to look and the lights were all on so I continued on my way. Later in the day I went to go out again and got about 2 miles before it kinda sputtered and died. I got it off the road and went home and got a DIC since that was my first thought. That worked sort of. It seemed to sputter and almost die when the heater fan came on, which happens a few seconds (quite a few sometimes) after starting unless you program it otherwise which I did. So it stayed running after I did that. But then when checking the brake lights again it sputters and dies when the brakes are applied and the reverse light is staying on.

So I heard tell of a ground in the boot under the CD changer and I will look at that.
Someone at a local scrap yard suggested that maybe the alternator is failing which kinda makes sense except I thought that would just outright fail not fade gradually in performance.

Another theory is that my 97 is jealous because it isn't a turbo and it doesn't understand that I got this other one to spare it from winter driving. So it put a curse on the 96.
The 97 is in PERFECT condition.
I am completely stumped.

With the reverse lights on all the time my theory is that you have a bad Transmission Position Switch formerly knows as the neutral safety switch. In the mid 80's the neutral safety switch became more than a switch that only let you start the engine in park or neutral. When OBD2 came along in the mid 90's this switch became the cause of all sorts of strange electrical problems most of which were addressed by early 2000 and 25 years later most people have forgotten about the odd problems this switch could cause.

Not to say that you couldn't have a bad DIC, alternator, battery, or ground, but a bad switch telling your body and engine computer that you're going backwards while you're actually going forward will affect everything from engine timing to automatic door lock operation.

Hi and thanks for your reply. So I guess what you are saying that a whole range of electrical issues could be attributed to this switch. I am definitively going to look at this.
Does your theory apply to manual transmission? And do you think it would be an awful idea to acquire one of these switches of a vehicle from a scrap yard?

Nothing wrong with a good working part from a salvage yard.

As with all "modern" cars, manual or automatic, a computer getting a bad signal is a confused computer. Two good things about manual tranny is you have no bands to fry with shift hang or slam shift and you can unplug this switch to see if your other problems go away.

Hi!
Took me a while to get back to my project car cuz of holidays and weather.
I decided to look at the easiest first. I the trunk to look at the ground that I'd heard about. It's attached underneath the bracket that holds the CD changer. Well there was basically nothing there body wise and the ground wire was just hanging out the trunk and the old terminal and bolt had become one. I put a new ring terminal on it found a solid clean spot and all the issues seem to have gone.
I did some searching for the transmission position switch and have one sourced from a local salvage yard. A new one is round $300 and the salvaged one is $50. So if this fix doesn't last or was just part of the problem I can still replace it.
Which leads me to another question, Where is this switch? I haven't located it by a visual search and can't find a good description online anywhere. It is also not in my Haynes manual.
I appreciate your help, you seem to be a font of information. Thanks