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  1. #1
    Setting Up Camp
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    Solution for 2020 Chevrolet/GMC Trailer TPMS not reading sensors on trailer

    There are actually three problems with the system. Stem size, not being able to set the tire pressure over 100 lbs, and not getting enough signal from the sensors to the receiver reliably. The stem size problem was resolved by sending them to a guy in Az. that changed them to the .625 with the same sensors. And on the 100 lb. limit. The sensors will read 102 lbs. if you set it to 100, my tires run at 110 lbs. so like someone else said at least I will know when they get below 100.

    But the system reading the sensors reliably is a real problem. I actually traded from a 2019 to the 2020 for this feature so I didn't need a separate TPMS, along with the camera's, 10 speed transmission etc. I saw on another forum that someone had removed the rear license plate with some success. Sure enough mine all read when I removed it. I opened a ticket with GM and they say it is an engineering issue and closed the ticket. So here is what I did to resolve it at least temporarily until GM comes up with a fix. Problem is lack of signal to the TPMS ECU located on a plastic bracket behind the rear license plate which is blocking the RF signal at 433.920 Mhz. GM part number for this unit is 84458180, I bought one from Ebay for $58 and modified it, removing the small wire antenna which is inside the 84458180 and adding an external dipole antenna crudely fashioned from some RG-58 cable. I mounted the antenna horizontally just below the square receiver hitch and it seems to work on my test run. One thing of note that I failed to realize on my first test run is that the tire sensor information is stored inside the ECU under the license plate. When you replace it you must relearn the sensors. Don't attempt this unless you have adequate bench equipment such as a Hakko solder removal tool or at least a Solder Sucker to remove the solder connections inside the ECU as the pins are molded into the plastic. The shield of the cable was attached to the small square and the plastic inside the cover was reshaped so I could temporarily move the original antenna connection and go back to OEM if necessary.
    Click image for larger version. 

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  2. #2
    Setting Up Camp
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    The antenna on the approximately 4 feet of RG-58 is just a 1/4 wave dipole antenna which is formed by pulling the center coax lead through the braid. Remove 6 1/2" of the jacket and pull the center insulated coax through and form the center and the shield into a "T" shape. I mounted it on a thin plastic sheet and attached the coax with nylon ties. I fabricated some hanger brackets and hung it about an inch below the receiver hitch. This way you have effectively just moved the antenna from it's original hidden location behind the license plate to a location below the RF shielding of metal at the rear of the truck.

  3. #3
    New Member
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    How has this solution been holding up? Have you made any other mods since?
    Could you post some more pictures of the completed antenna extension?
    Last edited by downtown brown; 09-04-2021 at 05:28 PM.

  4. #4
    Setting Up Camp
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    No other mods but covid has had us locked down just trying to be safe. We have only made one trip this year in May and June we did around 5000 miles to Co. from Fl. It lost a sensor a few times during the 6 weeks we were gone but only for short periods of time. It seemed that when turning at an intersection would be the most prone time to lose one. I used my old TST system as a backup. Its just disappointing that GM has not come up with a better solution. Even going through my dealer they say they know there is a problem but no resolution yet. I will try to add another picture of the antenna.
    Picture added. I could probably do a liitle better at it being stealthy but I got lazy. Painted black to help in that respect.Click image for larger version. 

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    Last edited by Thunderbolt; 09-05-2021 at 07:42 AM. Reason: add pic

  5. #5
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    Thanks for the update, I'm thinking to doing the same modifications in the near future, I will post my journey accordingly.

  6. #6
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    Thunderbolt….

    I was wondering if you could clarify a couple of details to this mod as I currently have my TTPMS module torn apart and am in the middle of this mod which by the way THANK YOU for posting this solution!!

    My questions are:

    1. You said you connected the shielding to the small square. I am assuming your talking about the braided portion of the cable. What small square did you attach/solder the shielding to? One of the two small squares by the hole you have the shielding coming through?

    2. Am I supposed to solder the core portion of the cable to the original OEM internal antenna solder point?

    Thank you!!
    Last edited by SierraJBravo; 09-19-2021 at 04:45 AM. Reason: To add info

  7. #7
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    Thunderbolt

    Just curious if this is still holding up bought a 2022 gmc and same issue with no resolve from GM unless yall have heard anything? Was going to do this setup didnt know if you had more photos? Thanks Thunderbolt!

  8. #8
    Setting Up Camp
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    Quote Originally Posted by Huskers View Post
    Thunderbolt

    Just curious if this is still holding up bought a 2022 gmc and same issue with no resolve from GM unless yall have heard anything? Was going to do this setup didnt know if you had more photos? Thanks Thunderbolt!
    Still using it and it is working. What other photos would you like? Another GM problem I also discovered is that when I took the tailgate off to put a truck camper in the bed, I had to add an external camera to the original connector because none of the cameras work without the one on the tailgate. They aren't very helpful at GM. I also tried to get my dealer to help get an update to the GPS system so I could put in my height with the 5th wheel attached. No joy with them or trying to put in a request myself.

  9. #9
    Setting Up Camp
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    Quote Originally Posted by SierraJBravo View Post
    Thunderbolt….

    I was wondering if you could clarify a couple of details to this mod as I currently have my TTPMS module torn apart and am in the middle of this mod which by the way THANK YOU for posting this solution!!

    My questions are:

    1. You said you connected the shielding to the small square. I am assuming your talking about the braided portion of the cable. What small square did you attach/solder the shielding to? One of the two small squares by the hole you have the shielding coming through?

    2. Am I supposed to solder the core portion of the cable to the original OEM internal antenna solder point?

    Thank you!!
    Yes either of the two small squares is fine. The center of the coaxial cable goes to the original antenna connection point. Sorry for the delayed response.

  10. #10
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    Do you have anymore photos?

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