2005 Denali No crank no start

[cooki3mnster]

Hey guys,

A friend of min has a 2005 Denali and a few days ago had a no crank no start situation. He asked me to help and I found that the battery was only holding 2.63vdc. I thought easy peasy a new battery later and we are good to go. He just called me today saying he has the same issue. I have yet to go check it out this time around. Anything I should look for? I have a feeling the alternator might be at fault.

 

[OR VietVet]

Connections at battery and corrosion down the cable insulation. Check connections at starter. Check grounds thoroughly. Check for a draw and yes, could be alternator that is also causing draw.

 

[Erickk120]

check battery voltage. Also if you get it running, check what the alternator is putting out and make sure its charging the battery. If below 13v under load then I would suspect bad alternator.

 

[rockola1971]

Shorted diodes in the alternator will run a battery down overnight. Alternator of course not charging at all could be a culprit. The most common problem of our chassis is the ground behind the engine on the firewall getting corroded or at the engine block rear also. The ground under drivers door on chassis just meeting where the firewall starts is also a culprit. The bad ground cause the BCM to do crazy whacked out things like not goto sleep after the last person out shuts the door. The BCM will kill a battery over night and eventually kill the battery for good with discharge/charge cycling. Silver migration on the instrument cluster can kill a battery over night also. Is the IC working properly?

 

[Fless]

Shorted diodes in the battery alternator will run a battery down overnight. Alternator of course not charging at all could be a culprit. The most common problem of our chassis is the ground behind the engine on the firewall getting corroded or at the engine block rear also. The ground under drivers door on chassis just meeting where the firewall starts is also a culprit. The bad ground cause the BCM to do crazy whacked out things like not goto sleep after the last person out shuts the door. The BCM will kill a battery over night and eventually kill the battery for good with discharge/charge cycling. Silver migration on the instrument cluster can kill a battery over night also. Is the IC working properly?

FYP, and agree.

 

[Doubeleive]

dead battery always= check the alternator
at startup you should have 13.4v minimum (at the battery)

 

[cooki3mnster]

Took another look at it and it was indeed the Alternator. Jumped the truck and brought it up to 2000 rpm and Alt was only putting out 8.368vdc. Swapped out with a new unit and we are good to go.

 

[Fasair]

Hi guys, new to the forum. 2004 Yukon XL Denali. May I ask what the BCM is please? Having this same issue. Thanks in advance.

 

[OR VietVet]

Body Control Module

 

[rockola1971]

Hi guys, new to the forum. 2004 Yukon XL Denali. May I ask what the BCM is please? Having this same issue. Thanks in advance.

BCM is the module that controls your lights going out after you shut the last door (also lights coming on), power windows, locks and mirrors, your factory security system inputs to the BCM and depending on options other systems too. Its under dash along side steering column.

 

[Doubeleive]

Hi guys, new to the forum. 2004 Yukon XL Denali. May I ask what the BCM is please? Having this same issue. Thanks in advance.

the bcm is unlikely to be your issue if you have a dead battery, bad battery/bad alternator.
if neither of those then start checking battery cables and grounds.
if it dies over night or over a period of a couple days then do a draw test, things like a aftermarket radio or amp or other things plugged into a cigarette port can kill the battery.

 

[rockola1971]

the bcm is unlikely to be your issue if you have a dead battery, bad battery/bad alternator.
if neither of those then start checking battery cables and grounds.
if it dies over night or over a period of a couple days then do a draw test, things like a aftermarket radio or amp or other things plugged into a cigarette port can kill the battery.

BCM not going to sleep causes the battery to die overnight also. Our chassis is notorious for this problem. A shorted output transistor in the BCM itself will cause dead battery overnight and also corroded or missing ground for the BCM will also cause this since it has no Zero reference available with a corroded or missing ground. And of course the shorted diode pack in the alternator or shorted cell in the battery will also cause the same symptom. A clamp on ammeter will rule the alternator out in like 15 seconds or less.

 

[Doubeleive]

BCM not going to sleep causes the battery to die overnight also. Our chassis is notorious for this problem. A shorted output transistor in the BCM itself will cause dead battery overnight and also corroded or missing ground for the BCM will also cause this since it has no Zero reference available with a corroded or missing ground. And of course the shorted diode pack in the alternator or shorted cell in the battery will also cause the same symptom. A clamp on ammeter will rule the alternator out in like 15 seconds or less.

this is why I also stated to do a draw test, just start pulling fuses until the draw stops
normally a dead battery is either a bad battery, bad alternator, corroded/bad battery cables/ground.
other more common causes are aftermarket equipment installed (causing a short) or something is plugged in.
BCM going bad is rare (not impossible) but it would be one of the last things I would check if nothing else panned out, just a process of elimination.