Jump to content

2020 Silverado Trail Boss - switches to sport modes, trailer towing mode, 4wd high and 4wd low on its own. Dealership is stumped

wacnstac
 Share

Recommended Posts

wacnstac Enthusiast

wacnstac

Posted
Posted

I have a 2020 Silverado Trail Boss which switches to trailer towing mode, all the different driving modes, 4wd high and low all by itself while driving down the road.  I can typically switch it out of these modes and back to normal by the switch on the dash.  Last straw was when it started trying to switch itself to 4wd low while at highway speed.  It didn't happen but was scary enough to take it in.

 

Dealership seems stumped.  They are talking about "rear actuator or rear carrier" and neither one of those make any sense to me.  Seems like they would be talking about a transfer case module or transmission module.

 

I'm concerned they are on the wrong track since all of these things are controlled by the switch on the dash, logic would say it was the switch or wiring to the switch.  They claim they have swapped in a different dash switch and the problem still happens.

 

Searching the internet doesn't yield a lot of info on a problem like this.

 

 

silveradosid Senior Enthusiast

silveradosid

Posted
Posted

i would be checking the wiring harness, there is a tsb on where the harness is known to rub through and cause problems. also check the ground strap behind the front right wheel thats behind the wheel liner

newdude Senior Enthusiast

newdude

Posted
Posted

Bad switch in the dash?  The drive mode selector and 4x4 controls are all a part of one single switch assembly.  Sounds like there could be an internal fault with that switch seeing its not only trying to shift 4x4 modes, but its changing to tow/haul mode (and sport and off road if you have/its doing that).  

 

Did they actually "swap the switch" for another to test?  Any codes present?  It doesn't seem like it would be a transfer case control module or transfer case encoder motor issue as its changing drive modes, and it doesn't seem like a TCM issue as its trying to control 4x4 modes and the TCM has no control over shifting the transfer case.  

 

4LO won't switch when moving anyway, truck won't allow it if you are moving in Drive or moving at any speed aside from 0-1mph.  

wacnstac Enthusiast

wacnstac

Posted
  • Author
Posted (edited)
12 hours ago, newdude said:

Bad switch in the dash?  The drive mode selector and 4x4 controls are all a part of one single switch assembly.  Sounds like there could be an internal fault with that switch seeing its not only trying to shift 4x4 modes, but its changing to tow/haul mode (and sport and off road if you have/its doing that).  

 

Did they actually "swap the switch" for another to test?  Any codes present?  It doesn't seem like it would be a transfer case control module or transfer case encoder motor issue as its changing drive modes, and it doesn't seem like a TCM issue as its trying to control 4x4 modes and the TCM has no control over shifting the transfer case.  

 

4LO won't switch when moving anyway, truck won't allow it if you are moving in Drive or moving at any speed aside from 0-1mph.  

Thanks for the great response.  Dealership claims they tried another drive mode selector switch on the dash and the same problem occurred.  I know that a 4LO switch is prevented when moving but having that come up at highway speed is very disturbing.  They said there are some codes present but of course they didn't tell me what they are.

 

When the vehicle does change modes on its own, it always obeys what I do afterward with the dash mode selector switch at least for a while.

Edited by wacnstac
newdude Senior Enthusiast

newdude

Posted
Posted (edited)
8 hours ago, wacnstac said:

Thanks for the great response.  Dealership claims they tried another drive mode selector switch on the dash and the same problem occurred.  I know that a 4LO switch is prevented when moving but having that come up at highway speed is very disturbing.  They said there are some codes present but of course they didn't tell me what they are.

 

When the vehicle does change modes on its own, it always obeys what I do afterward with the dash mode selector switch at least for a while.

 

 

Ask them for the codes.  Or if they ran a SAVI report, ask them for a copy.  Dealers are required to run SAVI reports if its under warranty but most of the time they run them just because.  

 

If they won't give you the codes (don't know why they wouldn't), do you have another dealer nearby that can print you out a SAVI report for your truck?  Or a trusted repair shop that can scan the truck?  Or a scan tool yourself that can read codes for the entire vehicle?  

Edited by newdude
wacnstac Enthusiast

wacnstac

Posted
  • Author
Posted (edited)

I had changed the battery to a non-OEM but AGM battery two winters ago.  Now I'm paranoid that the change may have caused some of these problems.

 

Dealership was focused on a bad Transfer Case Control Module and I am not convinced.   The TCCM but I don't think the TCCM is involved in trailer tow mode or the different sport modes which the vehicle likes to switch between on its own.  I told them if they don't find anything wrong with the switch on the dash, or the harness to it and verify the BCM and TCCM software versions, and a CAN bus ground inspection, I just want the vehicle back.

Edited by wacnstac
  • 1 month later...
wacnstac Enthusiast

wacnstac

Posted
  • Author
Posted (edited)

Dealership was of zero use in debugging this problem.  No codes = no fix.   The truck has now tried to put itself into terrrain mode randomly.  This mode is not even available on this truck as the truck has 4WD Low! and there is no separate switch for terrain mode or an option for this in the menu.

 

I'm thinking this definitely has to be an intermittent mode selector switch.  I think the way to narrow this down would be to remove the switch from the harness.   I am under the impression, that I could drive the truck this way knowing that I would not be able to change the modes obviously.

Edited by wacnstac
newdude Senior Enthusiast

newdude

Posted
Posted
1 hour ago, wacnstac said:

Dealership was of zero use in debugging this problem.  No codes = no fix.   The truck has now tried to put itself into terrrain mode randomly.  This mode is not even available on this truck as the truck has 4WD Low! and there is no separate switch for terrain mode or an option for this in the menu.

 

I'm thinking this definitely has to be an intermittent mode selector switch.  I think the way to narrow this down would be to remove the switch from the harness.   I am under the impression, that I could drive the truck this way knowing that I would not be able to change the modes obviously.

 

 

Pull it and try driving.  See what happens.  Worst case it turns the check engine light on maybe?  I suppose it could limp mode it but honestly, I've never driven one with the switch unplugged lol.  

Jay P Enthusiast

Jay P

Posted
Posted (edited)

Check this out. It caused some weird electrical issues with the 19 Sierra I had at the time. May not be your issue but pretty easy to check.

MC-10178357-9999.pdf

Edited by Jay P

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.

  • Forum Statistics

    250.4k
    Total Topics
    2.7m
    Total Posts

  • Member Statistics

    342,782
    Total Members
    8,960
    Most Online
    ShowMeShooter1332
    Newest Member
    ShowMeShooter1332
    Joined

  • Who's Online   1 Member, 0 Anonymous, 5,829 Guests (See full list)

  • Latest Articles

  • Posts

    • Jsdirt
      2027 GMC Sierra: Official Discussion

      By Jsdirt · Posted

      I was around and remember that era very well, so I'm calling b/s on that statement. If they were that bad no police department or taxi company would've bought a single one ... but they were used in both services (and fire) for DECADES. They were bulletproof and proven. Even the early 21st century ones weren't too bad! The early models were legendary.   Mine is proof, but people like atlas are blinded by agenda and refuse to believe facts right before their very eyes.   Even decades after they were built, a new generation started driving them, posting all their builds and shenanigans on Grandmarq.net and Crownvic.net. The failures would show up then, since they all were deep past 100k-150k miles by that point, and younger drivers tend to be a little aggressive, especially with vehicles than can lay a one-tire fire for as long as you hold your foot in it. They've more than proven themselves over the decades.   The only thing that'll really take them out is road salt. The bodies and sheet metal were garbage. A victim of the cheapout FoMoCo and GM have been partaking in before then, and since.   Today it's the stuff that counts - the undercarriage that rots away first!    GMs Caprice was no slouch either. Reliable as a stone ax - the opposite of what they build now.    
    • Jsdirt
      2027 GMC Sierra: Official Discussion

      By Jsdirt · Posted

      Let me know how your vehicles do in 10 years. You don't know ******, kid. 😂    There's a reason that Panther platform was used as police, fire, and taxi service for DECADES ... long before you were born, apparently.
    • davester
      Disconnecting Battery

      By davester · Posted

      If your connector also has a big lever to get the connector on and off, you don't want to force the lever either way, as it becomes a bigger problem if you bust the lever or the mechanism it works.
    • davester
      Disconnecting Battery

      By davester · Posted

      It's just useful to disconnect the battery to prevent odd shorting out when unplugging/plugging stuff together.  I also  touch the two cable ends together (after disonnecting) to drain the small amount of stored battery energy in various modules.   I believe the main system where you need to be more concerned with, so you need to do the above and then wait some time, iss when you are working on the air bag system, to prevent inadvertent firing of the air bags.   The in-cab switches are just that, plain switches, it's generally not a problem to swap them in/out.  For my '12, I'll get an error message on the dash if I power up the truck w them unplugged, but that's it (power up= turn the ignition on).   The ITBC located above the spare tire is a computer that manages the trailer brake system.  That is probably more important to have the battery disconnected.  It does have to be programmed to the truck, either before or after it's installed, for it to work.  For my '12, I had a very hard time reinstalling the main connector to it (IDK if yours is the same or not), it turned out the silicon seal was jamming up, preventing it from going on all the way.  I finally got it fully installed by lubing the seal with a bit of dielectric grease, then it slid on and latched in place easily.
    • BCGM
      Remote Start Noise 2024 2500 HD Gas

      By BCGM · Posted

      JR ! I just got the truck back from the Dealership today . The technician did a cold remote start on the truck this morning and it made the noise . It was determined that it was a starter issue and replaced it under warranty . Of course   it did not make the sound after a new starter was put in because the truck was not cold . We will we see what happens tomorrow morning when I start the truck cold  . Keep tuned !   Oh I found a video on YouTube of a cold start and it did the same thing your truck and mine do , I will see if I can find it and post it up

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...