Parasitic Draw

aaa_01yukon

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Hello all, new to the community and glad to be here,
I recently bought an 01 Yukon SLT 5.3l, equipped with 4wd and Onstar. The biggest issue I've had is the parasitic draw. The car draws around 50-90 milliamps at rest, whereas the factory spec is around 25-30 milliamps(according to ALLDATA). The car was stolen back in February of 2020 (and recovered), so the Onstar microphone, and GPS were disabled (the wires cut). I originally thought that the draw must be from the Onstar, but I disassembled the dash and disconnected the VCU and VIU, but I did not notice any change in draw. The only time when the draw dropped to within factory specification was when I pulled the RAP #2 fuse, which supplies power to some other accessories (locks, horn), including the Onstar VIU. I had to reinstall the RAP #2 fuse because the front passenger power window and power sunroof stopped working. I suspect it is with the RAP unit, or the BCM, but I'm having trouble finding exactly where it is drawing from. I should also add that the front passenger lock actuator does not work, and the front drivers side key cylinder is missing. The car also has a DEI remote start system (which is wired to an aftermarket switch for some reason), which does not work (likely because of the broken front passenger lock actuator and missing key cylinder). I know that is a lot of symptoms, but does anyone have any recommendations on what to do? Any tips or help would be appreciated. Thanks in advance!
 

MassHoe04

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I have seen posts, where bad grounds can prevent one of the control modules (the BCM, if I recall correctly), from putting accessories to sleep fully after the normal programmed time limit. HVAC, maybe radio, etc. They are supposed to "stay awake" for a while, then completely shut off. Poor or intermittent ground keeps interrupting the module and never gets to sleep. You hear it all the time, but make sure all grounds to the body, frame and engine are all clean and tight.

Parasitic draw is a frequent problem faced by many members. Since there is a lot of specific diagnostic procedures already documented on the forum... Do a quick search within the forum search window for "parasitic draw". Follow the recommended steps on what you need to look at and test. I'm not just hitting back with "go search" or "Google it". It's just that there are a few recent write-ups that have excellent step-by-step things to look at, measure and test sitting there now that you can get started with right away. Just looking to save you time in waiting for some responses to come in before you can go further in your diagnosis.

Members are always glad to help out, but the fastest way to get you going would be to have you check some of the information already posted first. Start with that first and report back all the information you can provide. Plenty of help with specific questions and tips as we dig deeper into your issue.
 

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Remove, inspect, and clean the two PCM connectors under the hood; watch for water migration in the lower part of the connectors.

Also, if you leave the radio on and turn the key off and remove it, and open a door, does the radio turn off right away? Try that individually with every door.

EDIT: one other thing, do you have automatic or manual HVAC controls?
 
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aaa_01yukon

aaa_01yukon

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I have seen posts, where bad grounds can prevent one of the control modules (the BCM, if I recall correctly), from putting accessories to sleep fully after the normal programmed time limit. HVAC, maybe radio, etc. They are supposed to "stay awake" for a while, then completely shut off. Poor or intermittent ground keeps interrupting the module and never gets to sleep. You hear it all the time, but make sure all grounds to the body, frame and engine are all clean and tight.

Parasitic draw is a frequent problem faced by many members. Since there is a lot of specific diagnostic procedures already documented on the forum... Do a quick search within the forum search window for "parasitic draw". Follow the recommended steps on what you need to look at and test. I'm not just hitting back with "go search" or "Google it". It's just that there are a few recent write-ups that have excellent step-by-step things to look at, measure and test sitting there now that you can get started with right away. Just looking to save you time in waiting for some responses to come in before you can go further in your diagnosis.

Members are always glad to help out, but the fastest way to get you going would be to have you check some of the information already posted first. Start with that first and report back all the information you can provide. Plenty of help with specific questions and tips as we dig deeper into your issue.
I will definitely look into the other posts, thanks for the tip! Regarding the grounds, that is something valuable to check out, I'm sure they're all dirty and rusted (it previously lived in Washington state). I'll come back to this later today or tomorrow after I clean the grounds, and share my findings. Thanks!
 
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aaa_01yukon

aaa_01yukon

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Remove, inspect, and clean the two PCM connectors under the hood; watch for water migration in the lower part of the connectors.

Also, if you leave the radio on and turn the key off and remove it, and open a door, does the radio turn off right away? Try that individually with every door.

EDIT: one other thing, do you have automatic or manual HVAC controls?
That is a great idea, I'll check out those PCM connectors. Regarding the radio, it turns off when I open and close a door (all of the doors), but only when I switch the key one click above the bottom. In left to right order, the clicks go from Half-Accessories(only radio on), to Fully Off(radio off), to Accessories(normal accessories mode), then Start. Before I found out about this, the battery would go dead if left for more than 12 hours, so the draw must have been at least 200 milliamps or more. I know from experience that this strange ignition key pattern is not normal amongst other Yukons and Tahoes. I have a diagram of it somewhere, and I'll post it if I find it. Regarding the HVAC, it's all manual controls. Thanks for the reply!
 

Fless

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A couple of other common causes of parasitic draw in these: one being silver migration (search the forums and/or Google it) on the instrument cluster circuit board. Using the voltage drop method across each fuse, you should be able to tell what circuit is staying awake, and your target of 25mA or so fully asleep is correct. There are charts to convert the voltage drop to current draw, so speak up if you need a link to those charts.

EDIT: Here's the one for mini fuses: https://m.roadkillcustoms.com/wp-content/technical-pdf/Mini Fuse Voltage Drop Chart.pdf


Mine was the driver's door latch, even though RAP worked correctly.
 
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aaa_01yukon

aaa_01yukon

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A couple of other common causes of parasitic draw in these: one being silver migration (search the forums and/or Google it) on the instrument cluster circuit board. Using the voltage drop method across each fuse, you should be able to tell what circuit is staying awake, and your target of 25mA or so fully asleep is correct. There are charts to convert the voltage drop to current draw, so speak up if you need a link to those charts.

EDIT: Here's the one for mini fuses: https://m.roadkillcustoms.com/wp-content/technical-pdf/Mini Fuse Voltage Drop Chart.pdf


Mine was the driver's door latch, even though RAP worked correctly.
Thanks! So the draw decided to go down to factory specifications, mysteriously. I'm thinking that I am just going to install a side-post battery disconnect, just incase things change down the road. Just out of curiosity, what would I clean the instrument cluster circuit board with that I suspect has silver migration? Thanks again for the help!
 

Fless

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I would start with isopropyl alcohol and a toothbrush. I like to use the 91% alcohol, but I think rubbing alcohol would be okay, too.

 

Doubeleive

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That is a great idea, I'll check out those PCM connectors. Regarding the radio, it turns off when I open and close a door (all of the doors), but only when I switch the key one click above the bottom. In left to right order, the clicks go from Half-Accessories(only radio on), to Fully Off(radio off), to Accessories(normal accessories mode), then Start. Before I found out about this, the battery would go dead if left for more than 12 hours, so the draw must have been at least 200 milliamps or more. I know from experience that this strange ignition key pattern is not normal amongst other Yukons and Tahoes. I have a diagram of it somewhere, and I'll post it if I find it. Regarding the HVAC, it's all manual controls. Thanks for the reply!
one click back is also accessory if you can remove the key with one click back then you need to replace the ignition switch, which you mentioned something is missing on it?
also I would check all these "cut" wires and be sure none are touching each other or on the body anywhere maybe tape them all off.
 

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