My first Dodge - 2004 3500 Quad Cab Cummins 4x4 4 spd auto. Fords and Chevys for 30 years and I am lovin this truck! Truck has less than 100k on it and is spotless. the only problem is the cruise control. Once it is set, it will shut off after only a few seconds. Then will not set at all. After shut-down and restart, you can set it again one more time after which it will shut off and not set again. Seems to hold about 10 or 12 seconds at 45 or 50 mph. Less than 2 seconds at 75 or 80. Have not bought a repair manual yet. Only had it a couple of weeks. Bad relay somewhere or does this sound deeper than that?

 

rear speed sensor.

Does your truck have abs? Does the light come on for it when your CC stops working. Just wait till your spedo drops to zero.

 

My 04 did this when the sensor on the brake peddle was going out. Cruise would just shut off by itself, the sensor was telling the computer I'd hit the brake. After a few days of this, it just went out all together.

Mike

 

my 05 does this sometimes while driving along will quit and wont work for awhile then will work fine for a few hours. figure its something to do with brake pedal sensor not sure

 

My guess is brake switch. Next time it does it, pull up on the brake pedal a little and try setting cruise again. If it works while holding up the pedal there is your problem.

 

Is the brake pedal sensor easy to replace? My 2004.5 is acting the same way. Works good until you have to hit the brakes to slow down then it works when it wants to.