2008 Tahoe loses power - electrical problem

[pacem]

2008 Tahoe LT, 188K miles, 5.3L

Sometimes - several times per month, when I park and turn off the engine, it starts clicking from the area where the door locks are.
The second thing that happens, I lose all power. No response from the key on. No lights, nothing. It's like the battery has been removed from the car.

I checked the voltage of the battery, it's good. Somewhere above 12V. It's charging when running somewhere around 14V imprecisely.

I have to remove the positive terminal from the battery, rebolt it and then everything starts again. My thought was one of battery cables has gone bad but if so, why does removing it and reinstalling it on the battery terminal works?

My other thought it's something to do with the security chip in it. I've had that exact problem when I got the car. The key would not do anything, it's dead. I had to get a key guy to reprogram it and now it's starting again. It's like the security chip in it loses contact with the computer module. I am not sure of the exact terminology but that's the gist of it.

Seems to be a common problem, here is a thread on it:
Especially the 2008 Tahoe entry, an identical problem:

https://forums.edmunds.com/discussion/5662/chevrolet/tahoe/chevrolet-tahoe-electrical-problems/p9

 

[clinebarger]

"The theft deterrent module (TDM) will command the security indicator be illuminated any time a fault is noted in the immobilizer system and when the engine starting is disabled."

A fault in the Immobilizer/Transponder/TDM WILL NOT cut electrical power to the vehicle! As stated above.....The dash will still illuminate....Along with other base functions like headlights, turn signals, HVAC blower, etc.
*Do you have base electrical functions when the truck is acting up?
*If not....Check battery voltage at pin 16 of the Data Link Connector, If No/Low voltage is found here, You have a bad connection.

My shot in the dark guess is.........

*You have a bad battery connection at the battery or underhood fusebox.
*The BCM is NOT waking up, The power mode master/Gateway is built into the BCM, As a side note.....Disconnecting the battery & reconnecting it WILL force a BCM wake-up!!

Possible BCM issues will take a good scan tool (GM Tech 2) to diagnose, So I recommend starting with connections first!

GMT-900 battery terminals leave a lot to be desired with their stupid cam style clamping mechanism, I know people hated the side post terminals on previous GM models. However.....They gave fewer problems. And when they did a good cleaning is all that was needed.

 

[Chris142]

Get the battery load tested. My wife's 04 Tahoe does all kinds of weird things when the battery is bad.

 

[GMBoy]

You cannot use the Tech2, must be the MDI tool to access the vehicle. From there you can diagnose. If you were close in Texas I would do it for you. (I am from MD!)

 

[clinebarger]

Originally Posted By: GMBoy
You cannot use the Tech2, must be the MDI tool to access the vehicle. From there you can diagnose. If you were close in Texas I would do it for you. (I am from MD!)


Incorrect, Tech 2 works on all GMT-900 trucks.

 

[GMBoy]

Originally Posted By: clinebarger
Originally Posted By: GMBoy
You cannot use the Tech2, must be the MDI tool to access the vehicle. From there you can diagnose. If you were close in Texas I would do it for you. (I am from MD!)


Incorrect, Tech 2 works on all GMT-900 trucks.



You are correct!! I read way too fast and thought it was a 2018. I work at the plant that builds them.

 

[WobblyElvis]

Some GM vehicles of that era have a problem with corrosion of the connector pins to the BCM. The fix is to remove and reinstall the connectors to the BCM. This scrapes away any corrosion temporarily. A corrosion preventative compound is applied if you want to make it last longer. Do this with the battery disconnected. Re-reinstall a couple of times. Costs nothing and may help find the problem.

 

[pacem]

That sounds like a good idea.