Got hit with a snowstorm, kinda halted the progress. I hope to spend some time on it tomorrow.

 

Well...long story short, pin 13 IS getting power. I only measured 7v, probably because the battery has been sitting and its cold as hell.

Let's just collect all the facts, so far:

-trans has power
-tcm has power and ground
-ecm has power and ground
-IMS is functioning correctly
-gear selection indicator has no box (does not highlight current gear)
-backup lights don't come on when shifted into reverse
-security light is NOT on

 

Do you have the battery on charge now?

 

Doyou have a way to possibly reflash the pcm/TCM ? Pulling it out my *** but maybe since you've checked everything else for proper operation that somehow something got corrupted. Or perhaps the battery needs a full charge ....regardless best of luck on this one. I'd be ready to put it in neutral and roll it off a cliff by now

 

Yeah its on a charger now, I've had it on a trickle charger the entire time but had to unhook it recently because i was shuffling cars around.

Trust me, if there was a cliff close enough...

And as far as I know, no. I can't reflash it, it won't even connect for me to scan for codes.

 

I am searching for a possible answer (the answer is somewhere in 7 haystacks...sort of speak)
You know when you tried the starter and jumped the terminals, it cranked no problem.
What if you tried that again with the key in the run position to see if the car will start as if the problem lays in the crank circuit everything else should work.
The indicator box was there before and may have nothing to do with the no start.

 

I did actually try with the key on, didn't work. It all turns over fine though.

 

Doesn't have a blue oval decal anywhere on it does it? If not good luck!

 

Just had a chat with a friend of mine senior tech also,we agree on possible data line there may be a module pulling all the others down. The only real way to test the datalines is to use a scope. With that said there is a way to isolate the modules and that is to pull the buss block/ pin they are the s 205, s206, s207 in the drawings, now seeming the indicator problem is there that area of the s 207 is a very good place to look carefully for a culprit. I will keep searching and let youknow if we can come up with more detail.

 

I know that this is probally no help but awhile ago i changed my alternator with a custom on with a ext. voltage regulator and the first time i started the car the dam thing got cranked up to 18volts and my dash lite up light a tree turned the car off got everything straight went to start up again and no crank and no shift indicator check all the fuses all good so i was sure i fried something but all i had to do was pull the power for 15min and she fired up so once again probally no help but its a idea

 

spy, pimpala brought something to the top of my head... How old is your battery?

I ask this because I have an 06 ss and it has had a situation since brand new and I have just come to live with it. The car was thru GM a dozen times and never was anything found.
Every once in a while you jump in and everything lights up but there is no start (usually cold out and the ON Star light on the mirror is out or red) never noticed the gear indicator.
I am now on my 7th battery! the simple act of replacing the battery solves the problem
each and everytime. The voltage is always between 12-12.3v, even after disconnecting the battery and charging to 12.6v in -20 after connecting turn the key on and there is less than 12.3. We decided it has to do with the current sensor somehow but cannot reproduce it. Even with a boost or charger on it I would be locked out from starting until I put a new charged battery in and it fires right up. This is basically a yearly thing and the Batteries are no cost to me. Originally these cars had a 525cca batt since then they went to 625 and now the latest is 640cca. The starter alone will draw 300+ amps on a warm day so if you figure a fully charged battery is 12.6 volts and 600cca and a 12.3v battery is 50 % of its capacity which would leave you 300cca.... you see where this is going.

 

I have doubted it was the battery. But it's not something I havent seen before. I'll get him to get a new one while I'm testing.

 

Yeah I feel stupid as it is right under my nose! The way they explained it to me is the systems calibration to preserve is so tight for the Impala it leaves very little room.
Here is some reading if your interested: http://www.gmls4.com/index.php?topic=2442.0

Aftermarket batteries are not recommended as the calibration requires certain parameters. my first few batteries were aftermarket and lasted just months before the tripped it again... then I went with the Delco pro 525 and it went almost a year, then the delco pro 625 and almost 2 years now I have the delco pro640cca about 4 months old and good to go each time.

 

and also when i had that problem my scan tool would not read so hopefully i atleast gave a idea

 

Weird I've been using a optima red top 900/1000 since I got the car with zero issues

 

You are correct weird... But remember it is an Impala issue and we also have a different battery to start with than the other LS4 cousins. My first replacement was a red top @ 3.5months by 6 months later the car died doing 70 and the battery blew the side out of itself. I know exactly why I did not remember this... ONE LONG HEADACHE and lots of time without the car, they went thru it a dozen times and never could it be found. So the outcome was/is the battery and the calibration as in the system has parameters to stay within and all will be good. Therefore I keep a spare and change it whenever I get the first symptoms (for me it is the OnStar light on the mirror it is either red or blank on first start) it will indicate normal after the car warms up. Then within days it will lock me out again. So guess who is real good at LS4 battery removal.
There is another variable to add, when this happens it is always cold -20*c/ -4*f or colder.

 

This car has a group 35 battery in it. Immediately tested bad. Interestingly, it appears it calls for a group 85 and my job doesn't even list a part number for that size.

 

Like previously mentioned not just any battery will do. A 525 cca will just buy you months, a 625cca will buy you a year and a 640-680 puts you at the max for calibration. autozone does list a duralast platinum AGM-35 680cca, terminals are on the correct side too. Your choice

As for the group 85 it will not fit as the height is 8" and the neg terminal will most likely touch the frame. The group 35 is 7.5-7.75"

 

Group 85 fits with room, actually went in easier than the 35 came out. Didn't help the problem though, but atleast the battery is good. Its 625cca. The battery was still under warranty, thats why we went with a replacement.

 

K, got a buddy I will try to reach tomorrow @gm