Forum Discussion

mokragleski's avatar
mokragleski
Explorer
Dec 12, 2015

Cruise Control Does not work when towing 5th wheen

Issue
I have a 2004 Dodge Ram 2500 5.9d. Starting in 2015, when I tow my 37 Ft. Larado, the cruise control will not work.

Cruise control works fine when not towing.
Replaced the transmission at 275,000 miles but issue existed before the change.
I normally tow with Overdrive engaged and has not been an issue before 2015.

I have been to 3 shops and they are clueless.

I am desperate for help as I have another long trip coming up shortly.

Suggestions seems to be, Don't tow with O/D on because it overheats the transmission and causes an error.
I would agree except nothing logs in the error codes on the engine computer.

Thanks
Tow Vehicles

26 Replies

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  • Me_Again's avatar
    Me_Again
    Explorer III
    Dec 12, 2015
    2002 got rid of the vacuum cruise control. It has to be brake light switch feedback from the trailer. Do your brake light come on steady when plugged in? Chris
  • YC_1's avatar
    YC_1
    Nomad
    Dec 12, 2015
    You may be getting a tiny bit of voltage feedback due to grounds between vehicles. As old biscuit is eluding to it could be in the umbilical or the connections on the trailer.

    I would open both ends of the umbilical if it is a jumper and clean and tighten. The same with every connections associated with the tow lights

    Are you traveling with running lights on? Do you have a charge line?

    Any minute amount of voltage sneaking back onto the brake light circuit even though not enough to light things up could cause it to shut off.

    Even check the electric brake grounds.
  • shepstone's avatar
    shepstone
    Explorer
    Dec 12, 2015
    You could try the vacuum hoses I had something similar many years ago, but I don't know if newer vehicles still use vaccum for cruise control
  • Old-Biscuit's avatar
    Old-Biscuit
    Explorer III
    Dec 12, 2015
    Brake light switch.....

    Has something to do with brake light circuit cause that is what trips CC off

    Brake controller/brake circuit wiring in receptacle ??????

    CC works until you plug in umbilical cord so check connections in receptacle and trailer plug and controller harness plug under dash
  • donn0128's avatar
    donn0128
    Explorer II
    Dec 12, 2015
    I know mine wont work until the motor is up to temp. It sounds like either a sensor or ECM is failing.

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