Where is my parasite?

[Uncle E]

I have a 2013 Yukon Denali, purchased 4 months ago. All was fine until 2 weeks ago. Sat for 4 days, would not start. Figured bad battery, replaced. Started fine for a few days. Then dead again. Jumped, ran fine, Payed close attention to volt gauge, Would charge at 14+ for a while then drop to 12 for a "longer" while, then go to 14+ again. Replaced alternator then as well. Checked old alternator when turned in for core charge, tested good. New battery, new alternator and same issue. 14+ to 12 to 14+ to 12, etc and dead battery after a couple days. Any suggestion?

 

[B-train]

The alternator is controlled by the ECM and functions that way for better fuel economy, less drag on the motor. Charges when it reaches a low threshold and then falls off once satisfied.

It sounds like you have a computer that isn't going to sleep after the retained accessory power circuit is supposed to time out. It could even be the RAP.

Couple tests:
1) sit in vehicle after running and shut off. Leave radio on and sit in vehicle w/o opening any doors and time how long it takes for the radio to shut off. Should be about 15 min. If you end up in there for much longer than that and still have radio and use of power windows, then you have a path to follow for the RAP.
2) Does the truck have any aftermarket add-ons (trailer brake contoller, etc)? Is there any additional no factory wiring under the hood?
3) do any lights stay on after closing the doors? Should dim out within a few seconds.

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

You are already receiving sage advice from the knowledgeable folks on this Forum.

 

[Uncle E]

The alternator is controlled by the ECM and functions that way for better fuel economy, less drag on the motor. Charges when it reaches a low threshold and then falls off once satisfied.

It sounds like you have a computer that isn't going to sleep after the retained accessory power circuit is supposed to time out. It could even be the RAP.

Couple tests:
1) sit in vehicle after running and shut off. Leave radio on and sit in vehicle w/o opening any doors and time how long it takes for the radio to shut off. Should be about 15 min. If you end up in there for much longer than that and still have radio and use of power windows, then you have a path to follow for the RAP.
2) Does the truck have any aftermarket add-ons (trailer brake contoller, etc)? Is there any additional no factory wiring under the hood?
3) do any lights stay on after closing the doors? Should dim out within a few seconds.

 

[Uncle E]

Yeah, went through the tests of those options, Radio shuts down consistently at about 14 mins and 35 seconds, no after market additions, and courtesy lights are about 7-10 seconds to shut off. Next step?

 

[B-train]

Oh boy......well now it's the crappy part. I hate electrical gremlins. Do you hear anything when the truck is off and it's quiet? Like a computer noise (hard to explain), I know mine will have some electrical noise after shut down and then I'll hear it click off a few seconds after exiting and closing the door.

A couple tests you can try to see kow big of a draw you have:
1) use an Amp clamp and see what, if any, is going through your positive cable after the truck has been off for awhile.
2) Check your battery voltage twice a day as it sits and see how quickly it falls off.

The last thing I would do myself would be to pull fuses and see if you get any feedback when reinserting them. If the truck is at rest, all the other stuff should be too. That may help to get a direction for the culprit.

 

[Fless]

You might want to start by letting the truck go to sleep and putting an ammeter inline with the negative cable, to see how much it draws when asleep. 50mA is the threshold; below that, it's acceptable but many of these will go below 30mA. The lower the better.

Instead of pulling fuses (and potentially waking up modules in the process), measure the voltage drop across each fuse's test points, and use the chart to convert to mA. Here's the chart for Mini Fuses: https://m.roadkillcustoms.com/wp-content/technical-pdf/Mini Fuse Voltage Drop Chart.pdf Any fuse that has a voltage drop is carrying current. Obviously you won't be able to check the Jcase fuses, but cross that bridge if you get that far.

Here's one of many videos on testing:

Sometimes a thermal camera can help find a warm circuit/fuse/relay. I have a very sensitive DC clamp meter that will ready mA on the negative cable without putting it inline, but those are somewhat rare.

 

[swathdiver]

Yeah, went through the tests of those options, Radio shuts down consistently at about 14 mins and 35 seconds, no after market additions, and courtesy lights are about 7-10 seconds to shut off. Next step?

Use the Tech-2 that you bought with the truck to run a parasitic draw test! LOL

Or get out a voltmeter and test light and pop the cover off the fuse block.