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12v tow power pin and trailer module

Discussion in '3rd Gen - 2007 - 2017' started by HawkX66, Apr 16, 2021.

  1. HawkX66

    HawkX66 Semper Fi!

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    17 Expy Platinum w/ HD tow package.
    Out of nowhere my 12v pin on the 7 pin harness went dead. The service manual takes you through some diagnostics and one of them is to test the trailer module. Where is it located?
    Is there something else to look at? The connector seems ok, but I'm getting 2.4v at a couple of pins. Kind of odd...
     
  2. Bigfishfin

    Bigfishfin Full Access Members

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    That circuit will be fused...
     
  3. HawkX66

    HawkX66 Semper Fi!

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    #48 40amp under the hood. Tested ok.
     
  4. 1970Maverick

    1970Maverick Full Access Members

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    Are you sure the ground is good? when you say you measure 2.4 volts at a few pins, how are you measuring this?
     
  5. HawkX66

    HawkX66 Semper Fi!

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    I tried with a separate ground and also tried using the connector ground. I'm using a multimeter.
     
  6. 1970Maverick

    1970Maverick Full Access Members

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    Full disclosure I don't have a tow package but I made my living chasing electronic/electrical problems. If I had a schematic it would be hugely helpful.
    Here's the only other thing I can think of, is there a relay that is part of the towing circuit?
     
  7. HawkX66

    HawkX66 Semper Fi!

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    Once I pull out the schematic I should be able to trace it. I went to school for electronics years ago. I was mainly trying to find out where the module was and start there. The service manual doesn't show the location of course... My electric manual is buried right now. I'll have to dig it out.
     
  8. HawkX66

    HawkX66 Semper Fi!

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    Here are the pages from the Wiring Diagrams manual if anyone comes across this thread and wants to see them.
    The Trailer Control Module is by the Parking Brake.
    I'm also adding a mod to have 12v at the pin all the time so you don't have worry about the factory "procedure" to get the 12v listed below. This is the same for F150. I'm actually going to put it to a switch, like an upfitter setup.
    I've also installed an Anderson plug at the hitch so I can have actual 12v power go to my trailer. Also nice to use for custom jumper cables.
    "For trailer charging to operate, the TRM must detect a trailer is connected and a brake pedal input before charging will be present at the trailer connector."
    This step is to get a constant +12V back to the 7 pin trailer connector since these trucks disengage the +12V power when the 7 pin trailer connecter is not in use.
    1. Cut a 6” piece of 16GA or bigger wire.
    2. Under dash on drivers side. Find trailer tow module. Locate both Orange wire (Pin 3 on C2498C Connector) and GY-RD wire (Pin 1 on C2498A Connector).
    3. Attach 6” wire between Orange wire (Pin 3 on C2498C Connector) and Green-Red wire using Scotchloks.
    This will activate a continuous +12V to the +12V power pin on the 7pin trailer connector.

    IMG_20210423_084242.jpg IMG_20210423_084148.jpg IMG_20210423_084051.jpg IMG_20210423_084045.jpg IMG_20210423_083848.jpg
     
    Last edited: Apr 23, 2021
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