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Discussion Starter #1 (Edited)
I am having a problem with my battery draining overnight. I have replaced the battery, and checked all wiring and aftermarket things that i have added.(remote start/alarm, amp, speakers, h3 power/heated seats, and radio, none of which has changed recently) I searched the forum and figured out that how to do a parasitic draw test, and am getting 170ma for the first 20 or so seconds, then 115-120ma after that. If I disconnect the radio fuse I get about 90ma. if I disconnect the TBC fuse and radio fuse, I get around 25-30ma. If I disconnect my fuse that controls all of my aftermarket add ons,(and the other two fuses) I get 4ma.
With the radio and add on fuse disconnected, I am getting 56ma, which will go back down to 4ma once I disconnect it.
I have searched the forum and found 2 other threads were people have experienced this problem with the TBC fuse pulling power after the truck is turned off, but neither of them posted a solution.
Hopefully someone can help me out here??? I'm lost as to what it could be.
 

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Tough deal to fix !!! Hope you Find the gremlin and chock the SOB !!!
 

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Discussion Starter #3 (Edited)
I was able to get it down to 86ma with my alarm/remote start completely uninstalled. I still think this is too high, so I pulled the fuses I have for my h3 seats, didn't change anything. I also pulled the fuse for my amp, and still didn't change anything. The only thing that is pulling power now is the tbc fuse(which I think is the bcm fuse), the radio(only like 20ma), and one other fuse that is only like 3ma.
Should I assume that the BCM is going bad?
Or is there a possibility that my ignition switch is bad and is telling the bcm to stay on?
 

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25 to 30 ma static current draw is normal and is mainly used for the PCMB memory backup.

I use to park my van for 2 to 3 weeks at a time and the battery did go down and starting was sluggish. I fixed that problem with a dash solar panel. Works great!
 

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Discussion Starter #5
25 to 30 ma static current draw is normal and is mainly used for the PCMB memory backup.

I use to park my van for 2 to 3 weeks at a time and the battery did go down and starting was sluggish. I fixed that problem with a dash solar panel. Works great!

I figured that the BCM would use some power, but when I disconnect the fuse it goes from 86-17, well over 30ma.(69ma)
I thought that Colorado shouldn't have more than 30ma parasitic draw, and with nothing aftermarket on the truck connected, I am getting 86ma. Is the 86ma enough to kill a battery overnight, or is it ok?
 

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115mA draw overnight should not kill the battery... What size are you running?

.115 x 24hr = 2.76Ah

Is something turning the BCM back on to prevent it from going to sleep?


Sent from AutoGuide.com App
 

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Discussion Starter #8
Well, I really suspect my BCM is going bad now. The windshield wipers are no longer working, or the motor that sprays the washer fluid onto the windshield. I don't think that the switch is bad because everything else on it works perfectly fine. I am going to see if I'm getting voltage to the wiper motor, and washer fluid motor, and if not then I know it has to be the BCM.
And yes, I checked the fuse and relays with a multimeter.

If you think it's something else, please let me know.
 

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I think you have a good hypothesis with the BCM malfunctioning -- or something causing it to malfunction. We know we have issues with these trucks getting a good ground, could it be related to this (I do not have a schematic in front of me)?

What is the main ground for the BCM?
 

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The ground for the Wiper/Washer circuits is G105, which is that small black box mounted on the fender wall, aft of the battery, outboard of the Brake Control Module.
 

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Discussion Starter #11 (Edited)
The ground for the Wiper/Washer circuits is G105, which is that small black box mounted on the fender wall, aft of the battery, outboard of the Brake Control Module.

Thanks, I will definitely check it before anything else.


I think you have a good hypothesis with the BCM malfunctioning -- or something causing it to malfunction. We know we have issues with these trucks getting a good ground, could it be related to this (I do not have a schematic in front of me)?

What is the main ground for the BCM?
I assume the ground for the BCM would be the one of the passenger side fender well. I will check that one too. Thanks
 
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