Parasitic draw.

Crazyfishinnut · Jun 18, 2025

Help parasitic draw. I have a 2020 Silverado 2500 6.6 gas ltz. After letting it sit from eight hours to three days, the battery is dead. I have taken it to the best two garages in my town. The one mechanic worked for my dealership. He was back-and-forth with the Chevrolet dealership. I ended up taking it to that dealership and after no certainty, I took it to my GMC dealer. So far they have replaced the starter ,the battery cables the ground to the PCM I assume done several attempts with a meter as I have done as well. No one can figure it out. Short of just throwing more parts at it with no rhyme or reason. About the time this started I also got a consistent check trailer connection on my dash. And it would not let me reset for several minutes into my drive. Whether that’s related or not I don’t know. I’m not sure where to go from here if my dealers can’t figure it out And the best mechanics in my area can’t figure it out.

mrrsm · Jun 18, 2025

Welcome to GMT Nation...

There are a few uncommon issues concerning Parasitic Draw (Drain) that may not have occurred to them in their Diagnostic Regimen:

(1) The Alternator: The Alternator is literally "An Alternating Current" Generator that requires either one or more Diodes to sort of "Peel Off" the DC Current using either one or more ONE-WAY RECTIFIERS. The problem becomes evident when a DC Drain happens if the Diode(s) go sideways... and thereby allow the Battery B+ Voltage to Bleed Right Back through the ordinarily controlled Alternator via this *Bad Control Valve* into Ground:

(2) Instrument Panel Cluster (Tin Whiskers) : Even though your vehicle is fairly contemporary, if the IPC was soldered up on the Logic Board with Non-Lead Solder...the TIN in the More EPA Friendly, Non-Lead Solder can actually grow long, microscopically thin and very flexible, very Electrically Conductive *Tin Whiskers* that can propagate along the various portions of the IPC Logic Board and Short Circuit the "HOT AT ALL TIMES" locations with a Ground. This sounds very Odd... but those Tin Whiskers... even as microscopically small as they may be... WILL Drain a Battery Down.

NASA Goddard Tin Whisker Homepage

(3) Rodent Infestation Depredation: As per @Mooseman 's recent Thread, GM has been using inexpensive "Environmentally Friendly" Soy Products in the manufacture of their Wire Insulation. As we all know... Mice and Rats LOVE to Chew on Wiring and Insulation under the hood in order to constantly wear down their ever growing Incisors...and we have ample proof that Short Circuits and Parasitic Drains can be the result:

(4) Thermal Radiation: In many cases... an intractable case of a Parasitic Draw can easily be disclosed by using a FLIR Infra-Red Camera. The reason for this is because whenever there is active current resistance in any electrical copper conductor occurring, the *Blockage* is dispersed as HEAT through a principle known as "PTC" Positive Thermal Co-Efficient. By using an IR Camera ...merely by scanning around the areas where known offending Modules are located... they will reveal themselves by their *Heat Signature". Allowing the vehicle to sit in the Dark and become "Stone Cold" and then examining all suspected problem areas may prove the fastest way to catch this "Electrical Draining Culprit":

IR Cameras abound over on Amazon in many shapes and performance sizes:

Amazon.com : flir automotive thermal camera

"Because... SCIENCE!"

PS... Just thought of a few other possibilities...

(5) Water collecting inside of the Tail Lights Lens Housings... especially in Tropical Areas during the Summer Storms.

(6) Short Circuits in the Dormant Wiring Harnesses under the Floor Carpeting.

(7) Leaking Sliding Sun Roof Panel and Door Seals that can send Rain Water cascading along the interior of the Pillars... and right down onto the Fuse Box at the corner edge of of the Driver's Side Dashboard.

(8) Short Circuits in or around the Seat Adjustment Switches.

The Linked WIKI PDF will better explain these ideas... and the Link to Amazon will show quite a few choices for IR Cameras:

Amazon.com : flir automotive thermal camera

Mooseman · Jun 18, 2025

You could try to do your own parasitic draw test. There are several methods that you can find great videos on. I like the battery negative cable disconnect method like in this video:

I also recently got a tester like this one to use with a multimeter that makes testing a lot easier and eliminates the wait time between disconnecting the battery and then reconnecting it with the meter in between and waiting for everything to go back to sleep.

https://www.amazon.com/dp/B0BL7DMT1Q/?tag=gmtnation-20

But before all this, I would imagine that the battery itself has been tested and/or replaced? If not, get it tested and replace if necessary. My 2021 Sierra's battery went bad in less than a year.

Crazyfishinnut · Jun 19, 2025

mrrsm said:
Welcome to GMT Nation...

There are a few uncommon issues concerning Parasitic Draw (Drain) that may not have occurred to them in their Diagnostic Regimen:

(1) The Alternator: The Alternator is literally "An Alternating Current" Generator that requires either one or more Diodes to sort of "Peel Off" the DC Current using either one or more ONE-WAY RECTIFIERS. The problem becomes evident when a DC Drain happens if the Diode(s) go sideways... and thereby allow the Battery B+ Voltage to Bleed Right Back through the ordinarily controlled Alternator via this *Bad Control Valve* into Ground:

View attachment 117342

(2) Instrument Panel Cluster (Tin Whiskers) : Even though your vehicle is fairly contemporary, if the IPC was soldered up on the Logic Board with Non-Lead Solder...the TIN in the More EPA Friendly, Non-Lead Solder can actually grow long, microscopically thin and very flexible, very Electrically Conductive *Tin Whiskers* that can propagate along the various portions of the IPC Logic Board and Short Circuit the "HOT AT ALL TIMES" locations with a Ground. This sounds very Odd... but those Tin Whiskers... even as microscopically small as they may be... WILL Drain a Battery Down.

NASA Goddard Tin Whisker Homepage

View attachment 117341 View attachment 117339 View attachment 117340 View attachment 117332

(3) Rodent Infestation Depredation: As per @Mooseman 's recent Thread, GM has been using inexpensive "Environmentally Friendly" Soy Products in the manufacture of their Wire Insulation. As we all know... Mice and Rats LOVE to Chew on Wiring and Insulation under the hood in order to constantly wear down their ever growing Incisors...and we have ample proof that Short Circuits and Parasitic Drains can be the result:

View attachment 117328 View attachment 117329 View attachment 117330

(4) Thermal Radiation: In many cases... an intractable case of a Parasitic Draw can easily be disclosed by using a FLIR Infra-Red Camera. The reason for this is because whenever there is active resistance in an electrical copper conductor occurring, the *Blockage* is dispersed as HEAT through a principle known as "PTC" Positive Thermal Co-Efficient. By using an IR Camera ...merely by scanning around the areas where known offending Modules are located... they will reveal themselves by their *Heat Signature". Allowing the vehicle to sit in the Dark and become "Stone Cold" and then examining all suspected problem areas may prove the fastest way to catch this "Electrical Draining Culprit":

IR Cameras abound over on Amazon in many shapes and performance sizes:

Amazon.com : flir automotive thermal camera

View attachment 117333 View attachment 117334 View attachment 117335 View attachment 117336 View attachment 117337 View attachment 117338

"Because... SCIENCE!"

PS... Just thought of a few other possibilities...

(5) Water collecting inside of the Tail Lights Lens Housings... especially in Tropical Areas during the Summer Storms.

(6) Short Circuits in the Dormant Wiring Harnesses under the Floor Carpeting.

(7) Leaking Sliding Sun Roof Panel and Door Seals that can send Rain Water cascading along the interior of the Pillars... and right down onto Fuse Box at the corner of the Dashboard.

(8) Short Circuits in or around the Seat Adjustment Switches.

The Linked WIKI PDF will better explain these ideas... and the Link to Amazon will show quite a few choices for IR Cameras:

Amazon.com : flir automotive thermal camera

This is not a normal parasitic draw. As I said two of the best mechanics in my area and two dealerships couldn’t find it. It’s like something’s coming on in the middle of the night after everything went to sleep. My question is is it related to The trailer connection, warning or the OK button on Will not working or the horn not working. After I drive it for a little bit the horn starts working. I am baffled.

mrrsm · Jun 20, 2025

Well... @Mooseman's direction toward using a Basic Digital Multi-Meter to measure "The Difference in Electrical Potential" in between those Tiny Contact Pins nested atop each of the Fuses... will be the Ultimate Arbiter... as the B+ Power MUST pass through any one or more of those Fuses to cause this Parasitic Draw. Patience and Due Diligence might reveal it... unless your Vehicle has been equipped with Non-OEM After-Market Equipment possibly installed by the Prior Owner.

Also, IIANM... @TJBaker57 has mentioned in Past Threads his use of a small, inexpensive Current Reading Digital "Fuse Buddy" inserted into specific Fuse Slots in the Power Distribution Center... to monitor for Parasitic Draw.

Mooseman · Jun 20, 2025

Check all your grounds. Although you're not throwing any errors or codes, these trucks are notorious for ground wires turning to green pus. I put the link to this video to start at the money shot:

Although yours is not exhibiting the same problems, maybe a bad or intermittent ground is waking something up and draining the battery.

Mooseman · Jun 20, 2025

And this may be a stupid question but it needs to be asked. Do you have any addon accessories, remote starter, chargers plugged in? Does your lighter plug always stay on? You can move the fuse for the lighter plug so it switches off with the ignition just in case you have something plugged in.

mrrsm · Jan 13, 2026

Sherwood's Video on using @Mooseman 's, @TJBaker57 's and @Blckshdw 's contributions -=on rescuing the Power Probe Voltage vs. Amps Cross Checking Charts=- and for using a Digital Multi-Meter ...is complimentary to their related Posts where PARASITIC AMPERAGE DRAW is *run down* by using Sherwood's Diagnostic Diligence ...and a Fluke 88 DMM:

movietvet · Jan 13, 2026

mrrsm · Jan 17, 2026

On Topic via "Eric O" from SMA (South Main Auto) showing the Low Amp Draw Tool called a "Fuse Buddy" for Folks who Do NOT have either an expensive Snap-On Vantage Pro Graphing DMM or a required Low Amp Clamp and Copper Wire Loop needed in order to visualize a Low Amperage Draw coming from a particular Module reading the Amperage Loss from a Pulled Fuse... AND... The related Power and Ground Circuit and Class 2 Network Schematics needed to Pin Point the Single Wire Splice Pack "Participants" found on the Network:

The ANSWER to "What Causes THIS" turned out to be the "Tin Whiskers" problem mentioned in Post #2 (Item #2) above Shorting Out the 12 Volts DC "HOT AT ALL TIMES" Power to the IPC Logic Board through Random Ground contacts on the IPC of this Trailblazer: