Serious And Weird Computer Issue With An 06 2500 Hd

demented · July 17, 2011

I posted this up in the Gm tech section also but i really could use some help here.

OK, I am hoping that someone will be able to help me with this problem because I am at wits end and really don't know what to do now except trade the truck in, and I really don't want to do that because I love this truck.

Anyways, Here is the history of what is going on.....

It started off about two months ago, just like any other time I plugged in my super chips programmer to adjust my shift firmness on my tranny because I just bought a new trailer and it was a bit heavier than my last trailer so I wanted to firm up the shifts a bit. Anyways, I plugged in my programmer and its started to think as it does and then I got an error code. Long story short, the computer in my truck was wiped clean, it had lost all the programming. I had to get the computer reflashed. So luckily I have a friend that works for a dealer and does costom tunes as well and came up and reflashed the computer on the spot and I was on my way, but he did tell me that it was not uncommon for the hand held programmer to do that once in a while. That is what I chalked that up to.

So I decided to take that programmer and not use it anymore and go with my buddy and have him make me a custom tune since he was able to adjust it just by stopping by his house and he could make the changes for me( he uses HP tuners)

He made the tune, and we installed it no problems. After running the truck a few weeks I wanted him to adjust a couple of parameters with the program so it would be better suited to my driving style. I stopped by once, and he made some adjustments, but it took a few times to get the program to go through. I drove the truck a few more weeks and stopped by again for him to make a few more changes and this time we were in for a nightmare. I drove the truck to his house. He backed up the file from my truck like he has done in the passed and we made the changes. But when we went to put the program back into the truck, once again, the trucks computer had lost the entire running program and needed to be reflashed. We ran a few tests on some of the modules and it all came back fine so we came to the conclusion that the computer may have a bad "memcal"? I think is what he called it. Anyways, I bought a new GM computer and put it in the truck. Tried to reflask it and we could not do it. so we thought we got a bad computer. So I got a computer from a donor truck, again the Tech II scanner could read the trucks computer but could not reflash it. So I took the new computer back to the dealer and had them reflash it on the bench and then we put it in the truck. Finally, we got the truck to start and run, however, we had a check engine light that said it had to relearn the crank trigger. We proceeded to do that but could not get the system to complete the test until the sixth time thru for some reason.

So I took the truck home and this weekend I decided to check some wires that I had a problem back in the winter time when some mice had chewed the insulation off of them. They never cut the wire but did break through the insulation. Among the half a dzen wires they chewed thru under the fuse box was the green wire that went from the aldl connector to the truck computer. So I spent the weekend and traced wires and rechecked everything to make sure I didn't miss anything and even checked the splice pack 205 under the dash, did an Ohms test of all the wires from the splice pack all the way to the computer and everything checked out perfect. I connected everything back up, hooked the battery back up ( yes I had the battery disconnected while I was doing all my checking) and I went to start the truck and now the truck wont run again. Its as if it lost its programming again!!!! I just don't now what to do. The only thing that may be off is the battery is a little weak but I do not have a tester to check it right now so I have to wait until tomorrow.

Does anyone have any ideas??? Someone mentioned I may have another module or a sensor that is bad that may be causing this to happen. Is that true??? I could really use some opinions or some good facts here.

desrtrat · July 17, 2011

my guess is a bad ECM. some of those hand held programmers have been known to fry a ECM..good luck in finding the issue

demented · July 17, 2011

my guess is a bad ECM. some of those hand held programmers have been known to fry a ECM..good luck in finding the issue

We already ruled out it being a bad ecm. I have put three ecm's in this thing including the original one and they all have the same problem. The problem I am having is some where within the truck itself and we are steering toward another module or sensor that is causing the problem. I can reflash the ECM on the bench at anytime and it will be fine, it is when we have to hook up the tech II through the truck and program or scan the truck or work through the harness or other modules is when we experience a problem.

HawkScot · July 17, 2011

I think you already suspect the wiring, that is my suspect also.

demented · July 17, 2011

I think you already suspect the wiring, that is my suspect also.

I suspected wiring at first but I spent the weekend pulling apart looms and harnesses and checking resistance and all the wiring to make sure that it was all good. I found nothing wrong with any of the wiring and I have been through most of it between the computer, fusebox and underdash area to the ALDL plug.

8.1HD/ALLISON · July 18, 2011

Have you been using the same Tech II? There could be a problem on the scan tool end. Like you said when you took it to the dealer, they programmed it no problem. We had some problems at the dealer I used to work at with scan tools sometimes.

C/K Man · July 18, 2011

There is so much that could be wrong here. You did say you had rodent damage to the harness. I would start there. Check every inch of it, even if it means removing it from the vehicle. It is possible you have a harness problem that is blowing your ECM. If the harness has many bad places, replace it. Check all gounds too, very carefully. After you are sure about the harness, then try an ECM with a stock program in it.

demented · July 22, 2011

Well I have been working at this thing and we think we have it figured out. Of all things, the cause seems to be an after market radio interface module. Apparently, anytime you do any kind of scanner, re flash, tuner, or any pcm or bcm work to the truck and have an after market radio in it, you MUST remove the fuse for the radio or all hell will break loose with the pcm and the bcm which is what had happened in my case. After installing the OEM radio back in and re flashing the new pcm and installing a new bcm the problem is gone. After a few search on the net, I found that same interface module has been the cause of other peoples problems as well in almost exactly the same manner as what I had experienced. I had actually found a bulletin from another interface company that acknowledges this same problem and makes dealers aware to remove the radio fuse when any pcm or bcm work is need to be performed. I wish I knew about this a while ago.