My 5.9 2004.5 AT truck has been acting weird lately. The brake pedal switch has been replaced so I know it’s now that. The shop who did the pedal said they checked the vacuum lines and pump and they all held either 12 inches or cm (I assume of water, but not sure)

The cruise will stay on at 65 mph, until I hit a hill. Then the cruise will kick off. Will stay on at 75 mph for only a few seconds, then will turn off.

Appears to me that it has something to do with how much load is on the engine.

This is with an empty bed, no trailer.

Any suggestions would be greatly appreciated.

Thanks.

 

If it's an 04 1/2 it's drive by wire,no vac needed .More likely a bad accererator pedal position switch or bad connection thru the steering wheelor a loose wire.The vacuum only operates the 4x4 axle disconnect and maybe the heater.

 

so why did the shop tell me they tested the cruise vacuum lines?
it's a shop that i trust...

 

I am having the exact same problem and its driving me crazy because I cant figure out what it is. The dealership told me its probably a hole in the tubing but I havent found one. And our trucks do run off a vacuum pump, its right beside the passenger side battery.

 

There is also a cruise control pod under the drivers side battery. Have same issue on mine. I gave up on the cruise.

 

Not on 04 1/2 -05 there drive by wire from the accelerator,no cable no ACCS under Battery. Look at accelerator pedal see if it has a six wire plug or a cable to box under battery,Check data tag is it a 305 hp or 325-600 ?

 

My 05 has the 6 pin wire plug thats it,Im only using the engine /tranny the rest is 05 F350 Ford.If yours has the cable it is most likely a vac leak,try a hand held vac pump (mighty vac) in place of the dodge pump,pull a vac and see if the gauge holds of leaks off if no leak the actuator must be bad or the pump is leaking off,I don't know what type pump Dodge uses so I can't help more.
you can catch me more on the powerstrokenation.com board under the engine conversion forums as hardint if I can help more. When I get home I will look at my buddies truck it has the remote APPS.

 

yup, it's got the 6 wire plug underneath the accelerator pedal
mine is the 04.5 325hp model

 

mine does the same thing. It`s worse since It`s been lifted w/37s , but it`s done it even when stock. It`s like the cruise is telling it to give it too much throttle to maintain speed. I just prepare myself for it , by turning it off ,when I know there`s an incline ahead.

 

Wow, now i am confused even more, not that it takes much. My motor has a mfg date of 4-2-04 and 325 on the cover. The body has mfg date of 4-04 in the door jam and it has a cat and 4" exhaust so i am pretty sure that would be a 4.5 model. It also has a cable from the top of the accelerator pedal to the motor and I can not find a 6 wire plug there. Sorry for the bad info, just stating what I see on my truck. Figures i got some betweener model. Who knows now.....

 

When towing my 5er and pulling a big hill or mountain my trans will downshift to maintain speed this is normal with the cruise on. I do not like the downshifting so I turn the cruise off. My XZT and later the Smarty helped to control speed better but they did not totally stop the downshifting. I turn the cruise off and drive by foot.

Now my cruise does not turn off unless I turn it off. The truck will resume cruise speed going down hill and shift again. If you can feel your pedal you can tell when the shifting starts is when the pedal is almost to the floor and speed is droping while climbing the hill.

This is when towing in OD. When I lockout OD I usually do not use cruise.

 

I had the exact same problem. It was a leak in my vacuum line.

 

i took my truck back to the shop today. they said that it runs great at 99 kmph but at 100 kmph the cruise kicks out.
thinkin git's the body control module

 

Well, all you 04 to 05 trucks are saying you have this problem. My 06 is doing the same thing. It has happend 4 times in a month to me. Am I the only later model pickup with the earlier model problem? It too is driving me nutso!

 

Yours is an electrical issue. 03-04.5 have a vaccum pump and dashpot for the cruisecontrol. (almost always a vaccum leak) The 05-07 are all drive by wire. Dealer will need to plug in and drive the truck, duplicate the problem and look at what is going on to diagnose.