One wire. A big lesson. It's done.

Thanks to ALL of the people who helped me troubleshoot this. In the end I learned how really helpful the forum can be.

Some really basic axioms were driven home........while my car now functions properly (other than now needing a tune)......had I followed the basics it would not have been nearly 7 months out of commission.

I will post my conclusions here soon......and I hope it will help many of my fellow enthusiasts.

 

For those of you just tuning in this is the final post detailing my battle with the Gremlin King.

Well, about now I feel as if I have been on an episode of Star Trek. The here to unknown Gremlin King has now, suddenly, decided to flee my car. I suspect it is now satisfied with the time, thought, and most of all, money I have spent in pursuing its destruction, and is leaving me with a bittersweet victory of sorts to savor.
Last post, had me debating a TAC module vs. a PCM vs. a BCM......and even an EBCM! So, suffice it to say, today's lesson I hope is useful to my many Corvette brethren on the Forum and beyond. And while you will see that my problem is solved, you will more so notice that I HAVE NO CLUE WHAT FIXED IT!
I began with a new/Reman PCM ($145) which arrived base programmed for my car. A quick and well done transaction. I programmed the VATS OVER 30 minutes and then repacked it. This was followed by a mail tune by Andy Green at A&A Corvette Performance ($100). It was replaced in its nook within a week and started right up! A very smooth and improved running motor that proceeded to yet again throw every code, DIC and IPC dash light. It threw in the quivering tach and speedo for good measure. Disappointment ensued. Further study, further thought, further talk with forum members and I added a second replacement module....a BCM ($125). This one obtained from Corvette Recyclers and off of a 2001 Z06. Programming was a cinch as my car had been purchased with all the bells and whistles that came standard on the Z06.....thus at this point no trip to dealer for RPO programming. I carried out the VATS PROGRAMMING handshake and she fired up beautifully. I drove her to the gas station..... and enjoyed the light show on the way! AND, my telescoping steering wheel would not function. I figured it one of the issues requiring RPO programming and ignored it for the moment. After filling the tank, I got in, reached down to move the seat forward and as I activated the switch, my seat stayed put, while the steering column telescoped out! Working the other seat switches I had a myriad of odd movements. "Up" switch layed the seat back down. "Back" switch pushed steering wheel back and caused bottom seat to elevate. Neat. Lights on, seat malfunctioning......what next? So now, a "new"PCM. A "new" BCM and the same issues and then some. Back to the drawing board.
This morning, based on ideas from last night, I set out to again clean some grounds.......G106, the EBCMs ground at left front rail and then lastly I pulled the battery out for the umpteenth time and looked over wiring, insulation and connections. Put it all back. Unplugged the front seat. My son and I went to run some errands.....lo and behold the car was now back to near complete (minus seat SCM) function........no lights. No quivering of the gauges. No nothing. She was like new! EXCEPT ONE THING. The next morning the light show began with the turn of the key. Got under the hood again and proceeded, with engine off, key "on", to burn my hand on some wiring. This wire I had originally asked my former mechanic to run down and check, which he assured me he had (and of which I have the $$$receipt). It was measured at 179 degrees in a cold engine bay. When I ran it, it seemed to have 3 branches. The middle, where the wiring branched into three was the ONLY part that heated up.(?) they where 3 separate pieces tied together. One end went down into the area around the starter, another end was attached to the front right rail ground and lastly the third went behind the motor, across to the left side of the bay and attached into a wire sprouting just below the oil sending unit wire on the harness. As I dug through the schematics and drawings I finally came across a non labeled wire that attached to a ground on the left rear of the LS1 block. Only thing is that I have an LS2 so I suspected that when my new motor was placed there was not a ground there(on the LS2) so they ran it to the ground at the right front rail with several others. Well, the resistance at the point where all three came together must have been quite high. I started the motor and then unplugged those three wires...the engine died. Two were well grounded but the one attached at the harness had +/- 7 volts running through it! Why? Not knowing why, I decided to split the grounded wires up, bringing the harness wire to the left front rail ground. Now, no hot wires! Car ran fine! And 2 weeks in and NOT ONE CODE ON ANY MODULE! That's all it took. So the gremlin is dead.
I spent money. Didn't need to. Nothing I replaced really needed it. So what are those axioms I spoke of? Well.......if you want it done right do it yourself. And.....check it yourself, then check it again. I hope you guys will realize that the modules really are fairly robust and not as prone as many think to failure. Most of our gremlins will eventually be revealed to be simple, easy to reach issues that were caused by previous tinkering. Mine was the rigged wiring placed when the new LS2 was placed. It was not the PCM, BCM, EBCM, or TAC MODULE. Lastly, a big shout out to Bill Curlee...not only an absolute fountain of Corvette knowledge but a perfectionist who pays attention to the details......and does not take shortcuts. So when he asks you to do something you have already done 10 times, know that their is a method to his madness. No shortcuts....and in the end you will not only find it but you will save ultimately in time. Take it from me. Go first to those places you have tinkered with before blaming the PCM, BCM, ETC...

This has been verbosely long, I know, but allow me one question to those electronic specialists out there......why is a wire that seems to be a ground have a small amount of voltage running through it? What is the function of a "reference voltage 5v" on various circuits? I have more questions but those will be better saved for new threads.......

Here's to a great forum, great people, and Bill Curlee!

 

It's funny how many of these threads I read that when the problem was finally solved it invariably involved a "poor" ground at some point. That "hot" wire was causing all kinds of grounding issues for the entire car, which would explain the bizarre things that were taking place.

The real question is, that wire with the 7v, where does it really go?

 

....to further your comment, those same ground issues, seem to always begin the same way. If the owner is lucky Bill will jump in, and his protocol will begin.....checking grounds. That part is long, boring and tedious and because of it people take short cuts by immediately blaming modules. Bill is rabidly against spending money without being sure, and rightly so. He will methodically continue checking wiring.....and with what I too have read, and now with my own experience under my belt he is usually correct. I'm proof positive. I hope that others will take the time to read this and perhaps take some hard earned and expensive lessons from it. Put your money on "grounds".

 

Here is an image from the 2001 FSM. I have arrowed the "wire". In this diagram it "seems" to branch from the harness. This corresponds to what I see on my harness. It is not a braided strap. G107 is its label, but recall that I have an LS2 now in this car. I don't know why they didn't use that ground, unless the LS2 block was without this particular ground point. Nevertheless, I took that wire and moved it to the ground point at the left front rail. All is well......but as has been noted why does that wire have voltage? And why does it function normally grounded? I sure would like an explanation from you electrical engineer types. Otherwise I fear I may have something else waiting to happen.