2005 Tahoe 2WD, 4.8L "No Crank Condition"

kmsbryans2018

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Recently my wife and I inherited her father's 2005 Tahoe. While sitting in a parking lot waiting on someone to meet us, the Tahoe decided to shut itself off. The instrument cluster was lit up like a šŸŽ„! The security light was on, the cluster read out said overheated, (found out that both of the cooling fans have stopped by hot wiring them to the battery and nothing happening.) Also flashing on the read out "power reduced", and something about the tire sensor. Once I got it back home I confirmed the engine is not seized by turning it with a socket and breaker bar on the crankshaft bolt. It has 1 stored P0606, 1 stored U0107,and 1 pending U0107. Because the security light is on, my stepson attempted while I was at work, the 2 wire snip snip bypass. Which I really didn't want šŸ˜”! This of course made no difference and since he knew I'd be upset he used blue butt connectors to put each wire back together and then closed the steering column back up. However, he left his wire snips under the hood and when I got home and found that the vehicle would do absolutely nothing I thought "dead battery", popped the hood and found the wire snips and then had words with him about cutting into any wiring harness on any vehicle.

I'm really not certain where to begin to tackle what's wrong with this thing. I recharged the battery and attempted the key relearn procedure. The security light is still on, possibly because those 2 wires aren't properly reconnected? I can solder and heat shrink them.. The cooling fans I will address after I get the thing running as they are not going to cause a no crank condition. Will the U0107 loss of communication with the throttle actuator control module cause a no crank condition?
 

kmsbryans2018

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I wrote this and then hurt my back and have not been able to get in the Tahoe and make the repair to the ignition wires that were originally mentioned. Hopefully, I'll feel better soon and I'll be able to move to the next step.
 

kmsbryans2018

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I saw 2 interesting things under the hood of the Tahoe the first was the grounding strap from the hood to the firewall was severed. The 2nd was that I noticed a slight green hue to the grounding strap that comes from the fire wall next to the brake booster and goes behind the engine. So there's some obvious signs of corrosion in the grounding system. I'm going to re-solder the 2 wires for the passcode lock system in the steering column this weekend. Which will eliminate them from being a possible problem.

At the same time I need to check all of the grounding straps & cables. Time to search for some diagrams that show where they're all located. If that strap has surface corrosion causing the green tint then who knows what other straps and cables are not providing a path to ground at all. If there's not a proper path to ground then we all know there's going to be problems with the throttle control actuators ability to communicate with the PCM.
 

kmsbryans2018

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My back is still not wanting to be bent over fenders and under the hood of a vehicle. However, I did manage to do a temporary repair to the snipped passlock wires. I soldered them back together and put heat shrink on each one. Then I got ahold of a WSM from seriousctbuyer on ebay for this vehicle. I've been looking through the almost 10,000 pages of this manual. Searching, hoping that I'll find something that will fit and link all of the symptoms together. Along the way I borrowed a friend's OBD2 bluetooth dongle and pulled the codes with the Torque lite app. Still have the P0606 and U0107 codes. Through my studies of the manual I received I could not find information on these 2 codes and I'm wondering is it possible for the U0107 code "loss of communication with the Throttle actuator control module" to be the cause of the P0606 which is to my understanding a generic code for an internal PCM failure? In other words can the P0606 be the PCM's way of saying hey, I can't talk with the TAC Module... I need to do that if you want me to allow you to crank over this engine. Please have the TAC Module report to me immediately or else I'm not letting you do crap diddly squat! Or is this more of an indication that a second PCM has gone bad on this Tahoe and that the root cause of the original failure is still lurking about and needs repair before a 3rd PCM is killed?
 

zora

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In your original post you mentioned the security light.
Is the security light still on ?
 

kmsbryans2018

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In your original post you mentioned the security light.
Is the security light still on ?
Sorry, I'm just getting back around to trying to figure this thing out. Yes the security light is on. When I got a copy of the GM work shop manual and looked up the section regarding codes I saw that the P0606 is an indication of an internal PCM failure. And when I looked up the security system it states that if the light is on and this code is present (among a short list of other codes that are not currently applicable) to first diagnose the code. However, I cannot find any further diagnostic information for the P0606 code. Such as how to know if the PCM is having trouble due to wiring, a sensor, another module not communicating, CAN Bus problem, etc. I tried reaching out to the guy I purchased the manual from to see if some pages are missing (I have a PDF) but that was fruitless.

I happen to have sitting in my barn a complete 5.3l including the PCM that came out of a junkyard 2003 Silverado. I'm curious if I could use that PCM to plug it in to the Tahoe and just try to get it to start. I'm sure it would run like crap if it works at all but I also don't want to accidentally fry a computer that's possibly a good one. Does anybody know if I can use that PCM in an 05 tahoe 4.8L as a diagnostic tool? I figure if it starts then I definitely have something frying computers and need to diagnose that as well as replace the PCM one final time...

Or am I being desperate and crazy for thinking this way?
 

zora

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PCM has to be programmed to the VIN of the vehicle.
 

kmsbryans2018

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I'm a bit unclear on wether to attempt using the PCM I have or not. I am aware and fully understand that ultimately any replacement PCM would need to be programmed to the VIN in order to keep things working like one big happy family in the long run. However, what I'm asking and what I'm still unclear on from your reply is will the PCM I mentioned allow me to at least get the engine cranking. Not necessarily starting, cranking and starting are 2 very different matters (cranking means the engine turns over and starting is another term for running). Right now it won't do anything at all. I have a code that says internal pcm failure and the security light is on. Which as best I understand the GM workshop manual the internal failure of the PCM can be causing the security light.

I have been working on equipment and vehicles for over 30 years. I did my first brake job when I was 9 under my dad's tutelage, I'm no stranger to wrenching. I just need some guidance once in a while as I have never wrenched for a living. I have been a certified parts technician, as well as a service manager for a number of years in both professions. I am familiar with reading and following service manuals up to the point that the information you need is simply not addressed in the manual and you have to rely on either the factory tech support or else your life experience as a technician. I have neither of those things to guide me in this particular matter.

Can anybody chime in and answer this question, will I harm the PCM I took out of the junkyard 03 Silverado, when removing the 5.3L for a different project, by hooking it up in this 05 Tahoe which has a 4.8L?

I'm just wanting to hit the key and see if it will crank over. But I don't want to damage this 2003 Silverado 5.3L PCM based on an idea that is in reality a hail Mary pass!
 
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