Forum Discussion

EnzoColorado's avatar
EnzoColorado
Explorer II
Oct 30, 2023

"Service Trailer Brake System" message on Suburban

In August during a camping trip, the message "Service Trailer Brake System" came on the dashboard when the trailer was not connected to the Suburban. I checked all the fuses and they were good. I hooked up the trailer to the Suburban and the message went away, the trip home was fine and trailer brake worked fine. Unhooked the trailer at home and the message came back on.

I checked the 7 pin connector in the back and everything looked good. I replaced the OEM Trailer Brake Controller thinking it had to be that thing. After replacement, the message stayed on whenever the trailer is not connected, and the message goes away when the trailer is connected to the vehicle. We have done two other trips since and the trailer brake worked fine each trip.

Hooked up the OBD II reader and there are no codes.

It feels like the Trailer Brake Controller thinks there is a trailer connected to the vehicle when there isn't a trailer? Any thoughts?
Tow Vehicles
  • Home_Skillet's avatar
    Home_Skillet
    Explorer II
    Oct 31, 2023
    Check for corrosion inside the back of the trailer connector, on the vehicle side.
  • ktmrfs's avatar
    ktmrfs
    Explorer II
    Oct 31, 2023
    if it is like the silverado, highly likely the problem is the manual trailer brake control lever on the dash. easy peasy to replace and often fixes the problem.
  • EnzoColorado's avatar
    EnzoColorado
    Explorer II
    Oct 31, 2023
    ktmrfs wrote:
    if it is like the silverado, highly likely the problem is the manual trailer brake control lever on the dash. easy peasy to replace and often fixes the problem.


    I have replaced the dash's trailer brake controller. Super easy to do. However didn't fix the problem.
  • EnzoColorado's avatar
    EnzoColorado
    Explorer II
    Oct 31, 2023
    Home Skillet wrote:
    Check for corrosion inside the back of the trailer connector, on the vehicle side.


    Thanks, will do.
  • valhalla360's avatar
    valhalla360
    Navigator
    Oct 31, 2023
    Might check the wiring near the trailer plug. If there is a short, it may have closed the circuit that the truck checks to determine if a trailer is attached but not all the circuits check out, so it gives you a warning. Particularly if the issue is intermittent.

    When the trailer is hooked up, all the circuits connect, so it thinks things are fine and enough juice may be getting back to operate the trailer brakes...so the warning goes away and your brakes work.

    Had an issue with our ford where the wire to one of the trailer brakes was chaffed and a strand was intermittently hitting the frame setting off a similar issue.
  • EnzoColorado's avatar
    EnzoColorado
    Explorer II
    Nov 01, 2023
    valhalla360 wrote:
    Might check the wiring near the trailer plug. If there is a short, it may have closed the circuit that the truck checks to determine if a trailer is attached but not all the circuits check out, so it gives you a warning. Particularly if the issue is intermittent.

    When the trailer is hooked up, all the circuits connect, so it thinks things are fine and enough juice may be getting back to operate the trailer brakes...so the warning goes away and your brakes work.

    Had an issue with our ford where the wire to one of the trailer brakes was chaffed and a strand was intermittently hitting the frame setting off a similar issue.


    Okay will definitely check the wiring behind the plug when it warms up this weekend. Thanks!
  • Thermoguy's avatar
    Thermoguy
    Explorer II
    Nov 02, 2023
    What year suburban? On my Silverado it was a steering stabilizer sensor. Not sure how it is related but twice I have had this problem and both times they replace the steering stabilizer and it goes away.
  • Krusty's avatar
    Krusty
    Nomad II
    Nov 06, 2023
    I agree it is likely a corrosion related issue and you should inspect the trailer connector and the wiring that connects to it. Not sure what modules you were able to read with your code reader, but typically they are only good for the PCM, so there could be several other modules with faults that you are unable to detect.

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