Motor refresh complete, now no crank, no start

I’m thinking a bad TCM or it’s connections. It’s strange how you got it to communicate but then lost it.

It all goes through the bcm including the can bus signals, thats still my bet. Lol

hagar said:

Not sure how competent the shops are around your parts, but you sound like you have more ability to fix the problem than almost all but the dealership themselves. Hopefully you bte the bullet and take it to gm, this will surely be one of the situations when paying more per hour, ends up with a smaller bill.

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Besides some free oil changes on new cars and some warranty work at a dealership I haven't taken my cars to a shop in 10+ years. I wasn't impressed by the skill at the dealerships either. A friend of mine is the manager of a local shop. I'm going to talk to him first and see if his shop can do it, he wouldn't steer me wrong. My next choice is the dealership, unless my friend has a strong recommendation for someone else.

Rocket Man said:

I’m thinking a bad TCM or it’s connections. It’s strange how you got it to communicate but then lost it.

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I'm hoping its not the TCM itself, those aren't cheap, plus it needs to be programed. Even when I had the communication to the TCM restored, I still had a no start condition. Plus, only 3 things happened in relation to the TCM from when I had restored communication to the TCM and when I lost communication with it again.

1. I finish torquing down the valvebody and reinstalled the pan
2. I added trans fluid
3. Wires got move around a little has I clipped things back in place, but no connectors were disconnected or reconnected.

I don't think 1 or 2 could have any impact on the TCM, but 3 certainly could.

hagar said:

It all goes through the bcm including the can bus signals, thats still my bet. Lol

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I kind of hope your are right, not only for your own validation, but also because I would rather have a bad module then knowing I have some bad wiring that I would always find questionable going forward.

I do efi systems and tuning for a living, i looked at the truck for hours going over grounds and wiring and such. The truck fully defeated me because my experience, and a laptop with hp tuners, wasnt enough to figure it out. i was un-equipped to solve the problem. Gm only charged buddy a half hour labor to install and flash the bcm including diognostic time. Never seen gm charge less than an hour, the truck didnt even come off the trailer.

I guess i am so involved in this because i couldnt do anything about my situation, and it was kind of embarrassing. My vested interest isnt validation as much as having a second chance at the exact same problem. Ha!

It would only validate what gm figured out that i couldnt.

I stopped by the shop today that has the Denali. They have re-verified everything I had tested, and to some extent they were surprised it wasn't any of the things I tested and that I was even able to accurately confirm as much as I did. Before throwing parts at it, they wanted to verify that the harness was all good. So far, all wiring has been good, and all signals on the canbus are clean. They have also disconnected all the other sensors that could impact the signal of the Canbus. Because a bad sensor or even injector can modify the signal enough on the canbus that it can disrupt the communication.

He has seen some abnormalities and performed other tests that keep pointing him back to the EBCM (Electronic Brake Control Module) as the source of the problem. The tech and I chatted for a good while, and I'm confident he will find the problem, and will have verified that there aren't other electrical gremlins that I need to be concerned about. Which I'm good with.

He is confident that it is not the ECM, so I'm sending the one I purchased back for a partial refund.

Yikes! cars have become so complicated, I am going to have to start accepting that allthough i "think" and my wife "thinks" i can fix anything when/if our 08 xl1500 Denali ever through a problem like this at me than to the dealer it go's! And than even the dealer with all the equipment and multiple techs can be challenged, IMO the only way for manufacturers to justify all this computer management BS is if the system could accurately diagnose itself and dispaly the necessary repair in plain english on the touch screen display and if it were wrong than the manufacturer picks up the tab! Now a cars demise is just as likely to be the result of electronic issues as mechanical. Sad reality.

thompsoj22 said:

Yikes! cars have become so complicated, I am going to have to start accepting that allthough i "think" and my wife "thinks" i can fix anything when/if our 08 xl1500 Denali ever through a problem like this at me than to the dealer it go's! And than even the dealer with all the equipment and multiple techs can be challenged, IMO the only way for manufacturers to justify all this computer management BS is if the system could accurately diagnose itself and dispaly the necessary repair in plain english on the touch screen display and if it were wrong than the manufacturer picks up the tab! Now a cars demise is just as likely to be the result of electronic issues as mechanical. Sad reality.

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It’s been that way for a couple decades or longer.

Its alive! The tech isolated everything, and finally determine that it was the TCM that was causing the problem. I guess kind of obvious, but I'm glad they took the time to determine it was specifically the TCM as the TCM was not cheap. Bad news, they noticed low oil pressure after it started which is frustrating since its a new oil pump, pickup tube, gaskets, etc. Hopefully just a bad oil pressure sensor.

Finally! LoL Good to hear!

Good to hear for sure. Curious as to the pressure issue.