Battery drain

I’ve been through hell with my 2004 Tahoe z71 it’s a long story but I’ll try to keep it as short as I can. It does not have automatic hvac controls

Years ago I had a remote start and touchscreen radio put in by a reputable audio shop and I think that’s where my issues began but not sure

I needed up having all that taken out but that shop

It’s ate up about 4 batteries including a yellow top and red top optima and has cost me thousands in repairs at different shops to no avail.

Latest was last week the last shop said I was drawing more milliamp from my instrument cluster so that was fixed and once again put a new battery in it but the battery will read 12.3 volts the next day so I called that shop and they assured me there were no more draws

So I asked them if I the audio shop had not removed everything like interface if it would cause a draw and he said yeah it’s possible as he did not specialize in audio

So I took it back to that audio shop and they didn’t find any draws but said that I should have a voltage drop test on the whole circuit. he said that my alternator is putting out 13 volts. I called the last shop and told them what the audio shop said and he said that something would show up on the dash?

This car is not a daily driver. Any ideas why the battery is losing voltage overnight?

I have had the same random battery drain over the past two years, did the same things, alternator tested, new battery, etc. I finally figured out that the BCM ( Body Control Module) which is supposed to sleep when the vehicle is off, is not going to sleep all the way..due to it “thinks” that my stereo is still on. In order to fix this, you can have the BCM replaced, or you can take it to a shop to have the old one re-flashed, or you can unhook both battery cables from the battery, leave them off overnight. Next morning, put them back on and this will teach the BCM to go to sleep when it is supposed to. A re-flash here in my area is about 200.00 so I would try the battery route and see if it resets the BCM first. Good luck .

Start with a parasitic draw test to see what the draw is after your cluster was fixed.

Sackett2622 said:

I have had the same random battery drain over the past two years, did the same things, alternator tested, new battery, etc. I finally figured out that the BCM ( Body Control Module) which is supposed to sleep when the vehicle is off, is not going to sleep all the way..due to it “thinks” that my stereo is still on. In order to fix this, you can have the BCM replaced, or you can take it to a shop to have the old one re-flashed, or you can unhook both battery cables from the battery, leave them off overnight. Next morning, put them back on and this will teach the BCM to go to sleep when it is supposed to. A re-flash here in my area is about 200.00 so I would try the battery route and see if it resets the BCM first. Good luck .

Click to expand...

Thanks for the tip. Disconnected both terminals a couple hours ago. Also

Sackett2622 said:

I have had the same random battery drain over the past two years, did the same things, alternator tested, new battery, etc. I finally figured out that the BCM ( Body Control Module) which is supposed to sleep when the vehicle is off, is not going to sleep all the way..due to it “thinks” that my stereo is still on. In order to fix this, you can have the BCM replaced, or you can take it to a shop to have the old one re-flashed, or you can unhook both battery cables from the battery, leave them off overnight. Next morning, put them back on and this will teach the BCM to go to sleep when it is supposed to. A re-flash here in my area is about 200.00 so I would try the battery route and see if it resets the BCM first. Good luck .

Click to expand...

Thanks for the tip. I disconnected both negative/positive a couple hours ago

When I reconnect the cables, is there any other steps I have to take to make sure the BCM was reset?

Also the audio shop said my alternator was putting out 13 volts. Today when I started the car with the voltmeter the battery jumped to 15 volts so does this say the alternator is doing its job or not necessarily? Before I started the truck, my battery was at 11.9 volts so it dropped more again over night. Not sure how it even started the truck as I thought it needed about 12.4 bolts but maybe because it’s a new battery?

Michigan said:

Thanks for the tip. Disconnected both terminals a couple hours ago. Also

Thanks for the tip. I disconnected both negative/positive a couple hours ago

When I reconnect the cables, is there any other steps I have to take to make sure the BCM was reset?

Also the audio shop said my alternator was putting out 13 volts. Today when I started the car with the voltmeter the battery jumped to 15 volts so does this say the alternator is doing its job or not necessarily? Before I started the truck, my battery was at 11.9 volts so it dropped more again over night. Not sure how it even started the truck as I thought it needed about 12.4 bolts but maybe because it’s a new battery?

Click to expand...

Nothing further is needed once you hook the battery cables back up,fire it up . If the BCM has been reset by disconnecting the battery cables, then your battery will stop running down when the vehicle is off and parked. If it continues to run down, then I would ask around and get prices to have the Mechanic re-flash the BCM to reset it. Finally, if that does not stop the battery drain, you will need to have the BCM replaced. These type of problems are pretty common and it’s a shame that no recall was issued for them. My Tahoe is a 2010 Z71 and has had numerous, random electrical problems. One day, the rear wiper wouldn’t work, the next day it started working and has worked just fine since. I have been stuck so many times with a sudden no start after the Tahoe sat overnight, that I bought a Halo Bolt to jump start it whenever needed and I carry it in the console. The battery cables being off overnight will hopefully do the trick for you. Good luck to you.

How exactly has it been determined that the BCM is at fault?

This is the shops wright up of what they did for the parasitic draw a couple weeks ago

“battery dead after sitting overnight.
vehicle would not start in am, fully charged battery and performed draw test. found 170 milliamp draw, should be under 50ma. traced draw to IPC/DIC fuse (instrument panel cluster / driver information center). unplugged instrument cluster and draw dropped to 20ma. removed foglight fuse and IPC/DIC fuses. Ran 10a jumper fuse from fog light fuse voltage leg to IPC/DIC leg. Fog light fuse is ignition voltage, not constant, and will shut down power to the cluster with key removed. fog lights no longer function.”

I took it back in the same week because the battery was still dying. He then ran the jumper fuse to the trailer park brake so I now have my fog light back and he then determined the battery cell may have been damaged. I got a brand new replacement die hard Gold battery and have been having the same problem. Fully charged battery keep dropping down to 12.3 volts in a few hours and then down to 12.0 a few more hours sometimes.

I called him today and he said to remove the trailer light fuse that the jumper was connected to and to connect the jumper directly into that circuit and to monitor it but within a few hours again it dropped down to 12.3 volts from fully charged 12.6 volts. When truck is running it’s showing 15 volts which he said was normal for these trucks

I have no idea what to check for now as he said he didn’t see anything else. In the verge of taking to another shop but just dumping a lot of money into this thing. This has been going on for years

I tried the 24 hour disconnect for the bcm but same thing, battery lost voltage. If I had a bad bcm would I have other symptoms? I believe it’s been getting poor mpg from what it use to get

Pulling power for the instrument cluster from another switched circuit is kinda of band-aid fix, but works. Basically, the cluster will only have power when switch is ON instead of all the time.

So it sounds like you may have more than one source of parasitic battery drain?

This might sound like a stupid question but have you checked all your grounds? Whenever I've had issues I always check all my grounds and clean them completely, usually it works. Also, unhook your battery for a while. And check for corrosion. And upgrade the main ground straps. Upgrading the main ground strap used to be a standard thing back in the day. And maybe do the others the others as well. Also, how old is your coolant? And how old is the radiator? BCM is original? I agree that unhooking it will reteach it to go to sleep.

ZombieHunterYukon said:

This might sound like a stupid question but have you checked all your grounds? Whenever I've had issues I always check all my grounds and clean them completely, usually it works. Also, unhook your battery for a while. And check for corrosion. And upgrade the main ground straps. Upgrading the main ground strap used to be a standard thing back in the day. And maybe do the others the others as well. Also, how old is your coolant? And how old is the radiator? BCM is original? I agree that unhooking it will reteach it to go to sleep.

Click to expand...

Thanks for the tips and advice,

So since my last post, the battery kept dying, I did try leaving the battery disconnected for over 24 hours to research the bcm to go to sleep and still had dead battery

I took it to another local shop and they said the only draw they were getting was a draw from the Instrument cluster. This was without me telling them what the previous shop said so I thought that they confirmed the problem. Another diagnosis fee paid but he also quoted me $900 to have the cluster rebuilt. Said he had to “take it out and ship it out as nobody in Michigan rebuilds them” I said no thanks. Took it out myself and sent it out for less than $200 for the rebuild

Put the rebuilt cluster back in and dead battery still after a couple of days, this is without me driving the vehicle though. This has been my secondary vehicle after getting back from my brother but now it’s going to start being driven more.

Anyways then took it to the auto parts store to have battery and alternator checked and the diagnostic tool came back with bad diode in the alternator. I had the alternator and battery replaced with new ones 2 weeks ago (July 6) and so far my battery has been reading 12.5 volts after 48 hours of it not being driven when before it would be at 12.1 or less the next day after being driven and then drop more each day till no start

I’m hoping this is the final draw for this nightmare of dead battery and it’s crazy that all these shops over the years wouldn’t think to test the alternator unless this is a coincidence. The alternator that was in there had a sticker 07/06

I spent a ton of money on the truck over the years with electrical problems. The first week I bought it in 2017 I replaced the battery due to it not starting so I think the previous owner could have sold it due to having some issues for them. I don’t know how many batteries it’s ate up but it was a lot. I’m not tech savvy or mechanic savvy so most times I had an issue after nothing on here or YouTube worked for me then I took it to a shop. I can try doing basic things though with advice from people on this forum and YouTube

A previous shop in 2022 said I had a burnt out light that was killing the battery then days changed the light control module.

Anyways long write up but went through a lot and even paid a shop to take out my remote start and aftermarket radio due to a shop saying that it was causing a drain. Since then I had the radio put back in but lost the remote start.