Strange Electrical Problems - 08 Yukon XL

jtupper · October 4, 2013

I'm having some weird issues with the wife's Yukon. I will start at the beginning and try to be as detailed as possible. I need to get something done, but I don't want to take it to the dealer or some other shop only to throw parts at it without knowing what the issue is.

The first problem started a long time ago. I noticed aleternator whine through the speakers. Sometimes it was very loud, sometimes faint and sometimes not at all.

Later, the a/c would just kind of shut off for a split second. It wouldn't completely turn off, but it would just blip, kindal ike losing power for about 1 second and then keep going. Shortly after this, the radio would just turn off for no reason. It would stay off for a few seconds, then turn back on. I started looking at the battery and noticed one of the terminals was a little loose. I pulled them both off and tightened bach up real well. The problems went away for a while after this, except for the alternator whine. Coincidence or r elated to the problem?

ANyway, before long the problems came back. On top of this, sometimes when we would start the truck, the a/c setting would all be reset to 74° like the battery was disconnected for a while. It would take a very long time for the blend doors to get to the correct setting and it would blow hot for a long time. A few times I even had to pull over and turn the truck off and back on the get the temp to start blowing cold again.

Next, the battery died. It was less than two years old. I had it replaced under warranty. This had no effect on the issues described. I noticed a short while later that wehen sitting at a light, I tried to wash my windshield and the wipers were moving really slowly. I noticed the battery gauge would drop to about 10v, the surge up to about 14v. I finally decided to go have the alternator teasted. Everything checked out fine on the alternator, but the guy said the battery could use a charge. Keep in mind, this battery was less than three months old at the time (this was about two months ago).

The latest in this saga has all happened within the last two weeks. My wife was standing at the back of the truck and opened the back cargo door and the radio turned on for a minute, then turned back off. She was holding the keys in her hand at the time. Finally, she went to start it the other day and it was dead as a doornail. No click, no drag, nothing. She called me and I told her to go try again. I wanted to hear what it was doing. It started right up. No battery low indicator or anything.

Now I'm at the point that I'm worried my wife is going to end up stranded somewhere and I don't know where to start. Most of this screams ground issue to me. But, the battery needing a charge and the voltage going up and down makes me think something is up with the charging system.

Any advice? I was thinking of replacing the alternator anyway, but I don't want to throw parts at it either.

tjmaddela · November 16, 2014

I'm having the exact problems could you guys please tell us how you got it resolved?

jtupper · October 13, 2013

The new cable arrived yesterday. I still don't know where the end of the small wire coming from the negative cable goes. I assume I have to remove the front bumper.

Does anyone have access to a write-up on how to replace it from a repair manual? I'd hate to pull the bumper if I don't have to.

Deaddenali · October 19, 2014

Did changing the cables fix this? I could have written your original post, having the exact same problems. Thanks

jtupper · October 8, 2013

The latest in the saga continues...

The truck has been dead 3 times this week. Usually, I can leave it for a few minutes and it will start. This last time (last night) I left it for about an hour an came back and it was still dead as a doornail. I put the key in and left the door open so I could hear the door chime. As I began looking at the battery cables as soon as I barely touched the negative cable, the truck came back tio life and I could hear the door chime going off.

I came home and started looking around the interwebz and stumbled upon an Edmunds page with quite a few people with similar issues, although I can't find any talking about alternator whine. There are a lot of them talking about a dead vehicle and jiggling the negative battery cable and it suddenly works. Apparently, it is not uncommon to have a defective negative battery cable,

The bad part is most of them haven't found a solution yet. The fixes the dealers have tried range from replacing the negative battery cable, replacing the 175 amp mega fuse on the firewall, replacing the alternator, replacing the BCM and so on.

I think I am going to start with replacing the negative battery cable. Does anyone know where the small wire coming of the battery runs to? It runs down the frame rail toward the front bumper, but I can't trace it past that point. It looks like I might have to remove the front bumper.

gmtech4 · October 4, 2013

the alternator is a good place to start as it will stop the whine with a new one ,im pretty sure ,,,other peeps can varify or tell u im a crack baby lol

get the bcm scanned as well,or at least clear them after the alternator install and start fresh ,scan it later if it acts up ,,,,you will at some point take it in for a scan ,no guessing remember

load test the battery after a recharge

jtupper · October 4, 2013

I forgot to mention that I did a voltage drop test across the battery, battery to chassis and battery to engine and there was no discernable drop in voltage. Admittedly, I have a little POS voltage meter though.

How do you test the BCM? I'm assuming I need to take it to the dealer for that or will most shops be able to do that?

gmtech4 · October 4, 2013

its not testing ,its scanning for fault codes

change alt ,,,,scan and clear all codes especially BCM,,,,,,drive truck,if it happens again ,have it scanned again ,,,,you are starting fresh ,,you understand ?

any shop that has a decent scanner can access the BCM,