How To: Strange electrical issues with 14-18 Sierra/Yukon? Do this test first!

[BigBlueLB756]

Changed out the positive cable and now she starts better than new.

Thanks a ton!

Check's in the mail.

[2018GMC]

Update: I got the service stabilitrack error randomly on startup a few months after Dealer replaced negative cable and bumper to bumper warranty ended. 

 

Occasional codes of B127E, B127B, B1325, U0121, C0800, U0073

Replaced short positive cable from battery to junction box. All connections were tight. Cleaned ground on outside frame rail under drivers seat.

It's been 2 months and no random codes or stabilitrack. Next thing will be to replace battery if codes come back.

[2018GMC]

[2018GMC]

[2018GMC]

Well I'm out of ideas.

I still get a service stabilitrack occasionally, along with B127E especially if I turn truck off and then restart after a few minutes (like when in a long line at drive thru).

I also get a random service safety restraint system, airbag light, along with U0140 Lost communication with Body control module only if i leave a door open when truck warming up for several minutes. Shut truck of and restart, no message and airbag light goes off, all seems normal after that. 

[bsprtsgrp]

I had my battery (original) replaced last August. My vehicle is 17' and I'm at 27K mileage. Recently I've received 2 OnStar notifications that I had a Low-State of Charge on my new battery which I found interesting because I keep the car on a trickle charge if the car sits for an extended period of time. Called my dealer who installed the battery and they tested the charging system and are now telling me that the battery cables have high-resistance and need to be replaced.

[BlaineBug]

5 minutes ago, bsprtsgrp said:

I had my battery (original) replaced last August. My vehicle is 17' and I'm at 27K mileage. Recently I've received 2 OnStar notifications that I had a Low-State of Charge on my new battery which I found interesting because I keep the car on a trickle charge if the car sits for an extended period of time. Called my dealer who installed the battery and they tested the charging system and are now telling me that the battery cables have high-resistance and need to be replaced.

Could be true but it sounds like a bogus claim, maybe they're just regurgitating what some TSB says.  To actually test the resistance of the battery cables they would have to disconnect them all from anything they are attached to, and this includes all of the grounds and main power connections as well.  Are they really doing this?  And their suggestion is to replace every single battery cable?  What are the resistance ratings they are attributing?

PS, have you checked your passenger front frame grounding location behind the wheel well/wheel liner?

[rav3]

26 minutes ago, bsprtsgrp said:

I had my battery (original) replaced last August. My vehicle is 17' and I'm at 27K mileage. Recently I've received 2 OnStar notifications that I had a Low-State of Charge on my new battery which I found interesting because I keep the car on a trickle charge if the car sits for an extended period of time. Called my dealer who installed the battery and they tested the charging system and are now telling me that the battery cables have high-resistance and need to be replaced.

Our K2XX trucks are notorious for "bad grounds" due to corrosion at the connecting points to the body. Watch this video I'll post below. He shows a very good solution for this. I did  add (2) additional grounds a he shows just as a precaution on my '17. Original battery is 5 years old so waiting for it to go bad now & will replace it with a high CCA/Ah AGM battery. Be sure ALL yoyr body grounds are cleaned & add some dielectric grease to help stop corrosion at those points.

 

 

[bsprtsgrp]

1 hour ago, BlaineBug said:

Could be true but it sounds like a bogus claim, maybe they're just regurgitating what some TSB says.  To actually test the resistance of the battery cables they would have to disconnect them all from anything they are attached to, and this includes all of the grounds and main power connections as well.  Are they really doing this?  And their suggestion is to replace every single battery cable?  What are the resistance ratings they are attributing?

PS, have you checked your passenger front frame grounding location behind the wheel well/wheel liner?

The Service Manager is a friend of mine and he told me this is a known issue. Tech disconnected and tested the cables. I'll ask about the wheel well ground

[bsprtsgrp]

22 hours ago, bsprtsgrp said:

The Service Manager is a friend of mine and he told me this is a known issue. Tech disconnected and tested the cables. I'll ask about the wheel well ground

 

They replaced the Positive main harness (84528825), the short Positive (84494554), and the main Negative harness (84634109).

Edited March 12, 2022 by bsprtsgrp

[someguy1313]

@bsprtsgrp:  i know it's been a couple years since your last post, but I'm super curious if this resolved the issue??  

 

to all: 

2017 GMC Sierra 2500 WT and having sluggish starter speed. 

Battery tests as good, Alternator tests as charging. (tested with my load tester and also at two auto centers)

Super clean engine bay overall (i have not traced everything to the terminal points yet).   

 

I put the battery on a smart charger overnight and bring it to 100% and it spins the starter and starts fast, as it should. 

Two days later, the battery is down to 60% and spins slower but always starts. (has never dropped below 60%)

I've done this multiple times. 

While at idle and no accessories on it is showing 12.3 volts at the terminals and also at the alternator. 

With AC and Headlights on, it will show 13.6 volts at battery and at alternator.

 

Any perspective helps but looks like maybe I should run down these grounding points as a start? 

 

Thanks guys.   

 

 

[2018GMC]

3 hours ago, someguy1313 said:

@bsprtsgrp:  i know it's been a couple years since your last post, but I'm super curious if this resolved the issue??  

 

to all: 

2017 GMC Sierra 2500 WT and having sluggish starter speed. 

Battery tests as good, Alternator tests as charging. (tested with my load tester and also at two auto centers)

Super clean engine bay overall (i have not traced everything to the terminal points yet).   

 

I put the battery on a smart charger overnight and bring it to 100% and it spins the starter and starts fast, as it should. 

Two days later, the battery is down to 60% and spins slower but always starts. (has never dropped below 60%)

I've done this multiple times. 

While at idle and no accessories on it is showing 12.3 volts at the terminals and also at the alternator. 

With AC and Headlights on, it will show 13.6 volts at battery and at alternator.

 

Any perspective helps but looks like maybe I should run down these grounding points as a start? 

 

Thanks guys.   

 

 

Replace the negative battery cable. Mine had high resistance which was a common problem. That took care of 90% of my random “service stabilitrack” and other odd messages on startup. I’ve always had good voltage though. 

[BlaineBug]

14 minutes ago, 2018GMC said:

Replace the negative battery cable. Mine had high resistance which was a common problem. That took care of 90% of my random “service stabilitrack” and other odd messages on startup. I’ve always had good voltage though. 

I am always curious as to how high resistance was measured.  Was it measured with the cable installed, or was resistance measured with the grounding cable completely removed and disconnected from the vehicle?  And how many cables did you replace?  Including any grounding straps?

[2018GMC]

9 minutes ago, BlaineBug said:

I am always curious as to how high resistance was measured.  Was it measured with the cable installed, or was resistance measured with the grounding cable completely removed and disconnected from the vehicle?  And how many cables did you replace?  Including any grounding straps?

Search for voltage drop test on YouTube. My cable was replaced while under warranty. Cable looked fine but tested bad. I also checked all my grounds, cleaned them and no difference. 
 

My voltage will drop on long highway trips the eventually goes back to 14, but this is normal operation as the alternator is computer controlled. 

[rav3]

A simple check for you to do. Look at the Power distribution block on top of the battery & see if any of the "nuts" are loose over the 6 or so connections. I've seen this come up in the past where a loose nut caused a similar issue.

 

 

Edited August 1, 2025 by rav3