This morning I checked my 12v battery and I have an Oddyssey 48-720 Performance series Deep Cycle 723 CCA battery that I installed in April of 2019. The truck sat for over 36 hours without starting. I had 12.5v on the terminals and about the same when checking various ground points under the hood. I put my battery load tester on it and had plenty of CCA's and I still saw 12.5v under the hood when I checked everything after the load test. My issues prior to installing that battery happened when it was cold outside and my truck did not want to start because something was making the new Delco regular 12v battery drop below 11.5v and created a no start condition. I did not have any problems this past winter starting because of the good AGM battery. Unfortunately it did not fix my dash board resetting issue when it's cold outside. When I put that battery in I noticed my ground cable was swinging in the wind. I cleaned up the spot where it should have gone and put a fresh bolt in it and regrounded it. I'm not sure when it became disconnected because the truck had some work done to it. To give you some additional background about my truck I had my 6.0L engine replaced due to a bad bearing at 77K miles (thank you GM!) the Accessory DC Power Control Module was replaced at 148K miles as part of SB-10057008-504 (thank you again GM!) on 1/31/2019 and the hybrid battery pack was replaced on 2/15/2019. Currently my truck has about 178K miles on it and I had no check engine lights until recently. Today I also played with the battery cables on the battery. I put some twisting pressure on both cables and the positive cable connector did not move with some decent pressure applied. The negative one did move with similar pressure applied so I do not know if that means anything or not. With the factory style battery cables I do not believe I can make that connection any tighter because it has that swing arm on it and not a bolt to tighten things up. I have read online where some people make their own battery cables but my truck worked just fine for a decade on the factory cables so I would think if I ordered new battery cables they would work ok for the rest of this trucks usable life. Any input on this would be appreciated. I'd like to get this current issue resolved.

 

Lots of info on the internet about the battery cable crimps going bad on the GM trucks with several videos of the infotainment and dash resetting on and off.Maybe replace the battery cables and get the dash resetting issue resolved and then MAYBE the mysterious codes will go away too. Probably would be my approach if I were having this issue myself. If that resolves the dash resetting and the codes are still popping up I would go directly back to best hybrid for a redo on the used parts they put in your hybrid battery.
I had a weird thing on mine where the rear entertainment console went bad (kids actually broke it) the rear speakers would make a loud buzzing noise when I turned on the blinker or hit the brakes etc. It does not seem to take much to get the electrical system upset in these things.

 

I don't have an issue replacing the battery cables with new ones. I found some on ebay that should work. Would it be best to replace both positive cables? It appears the positive cable is split into two cables. See pic's below.

Also since I have owned the truck a couple of times a year I believe the Bose amp cuts out when the radio is on and you hear a brief popping sound and then the radio starts playing again. It happens so randomly and rarely I've just ignored it since the dealer could not reproduce it to troubleshoot it. Also I occasionally hear a weird high pitch sound that comes and goes. It's not the alternator noise I've heard in older cars over the radio in the past this is definitely a different noise and again it comes and goes very randomly and rarely. Even if the radio is turned off I still hear it so it might be coming out of the Bose amp some how.

If you have an Android phone I high recommend the Car Scanner app for $4. It shows so much detail about the Hybrid battery without having to buy more expensive tools or use a Tech Tool. It is even showing me the fan speed RPM's of the hybrid battery fan.

 

Replace all battery cables.
On the radio it took years for people to figure it out but the rear radio control unit is your issue with that. One of my kids hung their back back strap on a **** and busted it on the inside of the unit, that was my issue. The control is in a vulnerable spot especially when you have a middle rider and they play rough!
Here is a link to what you need but shop around I think only gave 100 bucks for one about a year ago.
Not a hard replacement just be careful popping off the bezel trim it tends to get brittle with age......

Note: My Tahoe does NOT have rear heated seats and all these replacements control units have those buttons but it works just the same, the heated seat buttons just do not do anything LOL

 

Thanks for the info I will look into that after I fix my current issue.

The new negative battery cable will arrive tomorrow but the positive cables will take a few more days.

I have an update on my situation. The last couple of days I was trying to get my Vxdiag VCX Nano and the Tech2Win software working on my spare windows 10 PC. For some reason I can never get it to work right after a new install so now that I have it working on this PC I hope to not make any changes for some time. Luckily today I finally got it working so I can talk to the trucks bozoputer more on that in a bit. During a long low speed test drive in the local cemetery yesterday using the Car Scanner app on my spare Android phone I could see the hybrid batteries warm up from high 70 degrees to over 100 degrees during my test drive and the fan never came on and my check engine light was on because of the DTC codes coming from the hybrid control module. Now that I have my Tech2Win working I cleared the DTC in the hybrid control module and after a restart I saw the fan came back on again using my Car Scanner app. I drove the car about 2 blocks and the fan turned off and a mile or so down the road later and the codes came back and the check engine light came back on. I drove it for a bit and I never saw the fan come back on. I shut off the truck and restarted it and still no fan. I cleared the DTC's in the hybrid module a 2nd time and restarted the truck. I drove it for a few miles and the fan stayed running. I stopped a few times and shut off the truck and then restarted it and the fan cam back on each time. So it appears if the check engine light is on and that DTC P0A81 is present in the system the fan module will not try to start up. If those DTC's are cleared it will try and start the fan and the fan will run.

I do not know how long I will be able to drive it before the fan stops working again but now that I have that Car Scanner app I can keep an eye on things until I can get my battery cables replaced to see if they play any role in all of this.

Also I noticed that when I use the Tech2Win to see the data from the hybrid control module I see an error come up saying the wrong car type is selected shortly after it starts to display data from the module. I can read data from other modules so I thought this was a bit weird. I try and adjust my vehicle settings from 2008 to 2013 for a GMC hybrid but each time I receive the same error. Is it possible the module needs to be configured for my 2008 Yukon? I do not know if they program modules or if they just plug in any GMC/Chevy hybrid truck control module and call it a day.

 

I get that wrong car type message too sometimes when using my vcxnano.

 

Probably would not hurt to have a full sequential module relearn done. A local garage did that for me when they replaced the ABS assembly. 100 bucks and everything is working great at least for right now Haha I thought about getting a tech2 and doing all this stuff myself but decided that it was not worth the cost and my time,ESPECIALLY after seeing them struggle for 2 days to get it done correctly. Support your local garage...................

 

First I just wanted to say thank you for everyone who commented on my post.

About 8 or 9 days ago now I used my Tec2Win tool to clear the DTC's that were stored in the Hybrid Battery Control Module and not just generically clearing the DTC's by using the Car Scanner app on my phone. Every since I did that I am seeing normal fan function as I drive the truck. I keep the Car Scanner app up and I watch the Live Data and I can see the fan is working. I'm not 100% sure or not if clearing the DTC's in the Hybrid Battery Control Module verses just generically clearing DTC's with the app made a difference or not but so far (knock on wood) it seems to be holding.

Last night I spent 3 hours swapping out all 3 battery cables on the truck. It was a fairly easy process once you have the items that are in the way removed. The day before I installed the cables I made sure to add a good amount of solder to all of the crimp points to make sure they were going to be a good solid connection for a long time. Once everything was back together the truck fired up and all was well.

I will continue to monitor the fan situation as well as the dash board resetting issue when temps drop. It's been hot and muggy out here the past few days so it will probably be a few weeks before the temps will drop and I can see if the issue happens again or not.

Thanks again to everyone for your input on this.

 

I have new cables as well where does the long thin neg goes?

 

The long skinny negative cable goes under the radiator support on the drivers side. It's hard to see because of the frame rail and the plastic support for the front bumper. I removed the 7 mm screws and the 10 mm bolt the plastic uses for support. There is a metal bracket held on by three 10 mm bolts that makes it difficult to see the cable so I removed it too. It is a nut and bolt combo so be careful not to lose the nuts if you take that off to get to the connector that faces the bumper cover. There is a 10 mm bolt that holds the two wires on it. I'm not sure where the other negative cables comes from but it lays against the radiator support and the negative cable from the battery goes over the top. I just routed the skinny negative cable over the frame rail similar to how the old one went in. Be careful when replacing the positive cable that goes into the big fuse box. The plastic is getting brittle on my truck so I'm assuming it's similar on your truck as well so take your time taking it apart. I had to remove the battery, the two metal brackets on the drivers side fender, the air filter box and the two pieces of plastic under the truck to get access to everything so I could swap out all of the cables as easily as possible. Since the one positive cable goes in by the inverter I played it safe and pulled the safety disconnect on the hybrid battery before touching the positive cables. If you reseat the safety disconnect plug properly you should have no issues when everything is done. I pushed the safety disconnect back in but forgot to slide the arm downward to complete the connection so it threw me off for a few minutes. If you don't do that you will get a service hybrid system message on the dashboard.