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2006 Sierra 2500HD SLT LBZ 4x4
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Discussion Starter · #1 ·
Having a couple issues recently
  • In the morning when I open the doors before I start the truck and even shortly after all my interior lights flicker and so do my license plate lights.
  • Randomly get service brake system (No ABS Light) when key on engine off for a quick second and then goes back to normal with my odometer. Only once did I ever get the loud ding ding dings associated with that.
  • LCD screen in the head unit randomly is either not on or very very dim when you start the truck. After about 5 minutes it goes back to normal
  • My battery gauge is about 12V for a minute after starting the truck. I know glow plugs and what not take a lot of juice but it was 80* out today. I am thinking it is not this.

Also if anyone has read my other threads I have other intermittent codes but I doubt this is part of them.
My main question is about that 12V on start up. Is that normal? I also know that this truck has the voltage regulator in the ECM iirc but I figured that it shouldn't be telling it to be that low when the truck is off right?


I plan on taking the batteries to get load tested this weekend. I would like to rebuild my alternator if that is an option but don't know much about it. A new one is about $200.

Any thoughts?
 

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2006 Sierra 2500HD SLT LBZ 4x4
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52 Posts
Discussion Starter · #3 ·
My driver side battery is 5/20 and my passenger side is 9/19. I'm in the ball park for new batteries. Previous owner didn't replace them both as you can see. They both test to 12.5 with a voltmeter though.

Found this old man ground. Definitely getting that taken care of this weekend, yeesh. If you look closely you can see that there are two ground wires in that one lug. Is that normal?
Automotive design Auto part Metal Carbon Automotive exterior
 

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Check the passenger side battery ground to the frame, and frame to the firewall.
 
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2006 Sierra 2500HD SLT LBZ 4x4
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52 Posts
Discussion Starter · #6 ·
So I found that I can just replace the boot and bolt instead. I will still be cleaning and going over the grounds.
Boot is Dorman 60300
Bolt is Dorman 60307

If you open the doors but don't turn the key all the lighting and stuff is normal no flickering and what not. You turn the key on engine off and the volt gauge will be at like 10V maybe go up to 12V and all hell breaks loose with the flickering lights. You turn the truck on and give it a minute or so and the flickering goes away and volt gauge is up to 14-14.5V.
I know the volt gauge isn't the most accurate and I will go back with my volt meter and test it as well. Just weird
 

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(I know you know all this ) As batteries get old, they may read 12.VDC static, but when a load is put on them they go down. a fully charged health battery will read 12.6 or more. I would bet, after you get those tested you will find they are weak, that and the ground you found, I'm sure your problems will be resolved. I replaced the batteries on my 2019 in 2021. They just don't make them like they used too.
 

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2006 Sierra 2500HD SLT LBZ 4x4
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Discussion Starter · #8 ·
@tobyhd02 I didn't even think about that for some reason. Yeah I bet that is my issue.

My battery in my other truck lasted exactly one year I believe before it lost a cell in it. You are right, they don't make them like they used to.
 

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I was so surprised with my 19, I figured the batteries would last 4-5 years like in the past... also, these trucks are so finicky about voltage/amps. Santa is bringing new batteries maybe!
 

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I just replaced both batteries in my 2015. They died fast after a long life. After 7 years and 3 months the XM radio quit working. Next morning deader than a doornail. So 7 years and 135,000 miles. I have no complaints.
 

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IMHO
-Have an auto parts store read the codes, including the ABS codes.
-2 New batteries are good place to start.
-Check the grounds for being clean and intact on the left side of the truck: In front of the engine to the frame, frame just under the driver door, and front of bed to frame.
-Check for a frayed ground somewhere. (I found the hot line to my trailer plug had over heated, melted the insulation, and created a short to the ground in the trailer hitch loom.)
-Check for any blown fuses.
-If still a problem, remove all the covers to the main fuse block and look for wire damage. (I found a mouse nest in mine.) Go here for the full story...

Good luck.
 

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2006 Sierra 2500HD SLT LBZ 4x4
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52 Posts
Discussion Starter · #18 ·
Yup bad battery. Bought two new AAA batteries.
Replaced the boot and bolt on the primary battery ground cable and replaced the bolt on the secondary battery positive cable.
The primary battery had the hold down block bolt broken off in the tray and no block in sight so I pulled the tray out (broke one of the tray bolts off at the head so that bolt is gone) and slowly twisted the bolt out. Wire wheeled some rust off and then repainted the tray and got a new block and bolt from Advance Auto.

Battery hold down kit DieHard P/N: 45165
Battery cable boot kit Dorman P/N: 60300
Battery cable bolt kit Dorman P/N: 60307
 

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2006 Sierra 2500HD SLT LBZ 4x4
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Discussion Starter · #20 ·
I did end up swapping out the LED bulbs and that also fixed my lights flickering issue.

My head unit still comes on dim so I am just thinking it is aging a bit. I planned on replacing it anyway with a 1factoryradio BT unit.
 
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