It's a 99 1500 5.9l auto. The cruise is going the same thing as the OP. I can turn it on, it stays on for about 30-45 seconds, then shuts off (the green light on the dash goes out). I cannot turn it back on unless I cycle the truck off then back on. Cruise will work while it's on though. I have gotten to the servo, I just need some daylight to test voltages to it now.

 

This is the other thread that was very similar.

https://dodgeforum.com/forum/2nd-gen...n-a-timer.html

 

Any particular action make the cruise turn off? All voltages to the servo come from the PCM. If cruise isn't active...... not sure you will see anything there at all. Grab the 98 service manual from here. Should be some troubleshooting hints in there.

 

Yup, grabbed the manual already. That's how I did the resistance check on the switches. Oh, and just for S&G's, the resistance is the same at the connector after the clockspring.

No, no particular action required for it to turn off. Just idling in the garage (with the door open, so I don't kill the felines), it will just blink out. I am still not sure about this but it might be thermally related. Initially, it can take about 45 seconds to shut off, as the engine ( and engine bay?) warms up, it will shut off quicker and quicker. Again, then I need to cycle the truck off before I can turn the CC back on. I have a set of used CC switches coming, they should be here Friday, then I can tell if it's something else. I get the part about the varying voltages to the PCM, depending upon which CC button is pushed. When it gets light out, I am going to tinker with servo. There is not much info on it in the FSM, just replace it, but I want to see if I can make it actuate or not, check for a short/open (especiallly as it warms up).

 

My cruise is doing the same thing as the OP, turning on for a short time, then turning itself off. This is meaning the green dash light, not activating or de-activating.


Truck is a 99 1500 4X4 auto


My resistance values for the switches are way different than what the FSM calls for. But now that I have hacked the switches apart, I will have to wait until I get the new (used) ones to re-test and post the values. I also get the same values after the clockspring, so it is probably not that either.


Meanwhile, while testing the servo for voltage, today it was not getting any (oddly, yesterday I was). Down to take a look at the brake switch. It is held in place by 2 keys. It kind of locks in place with a 1/4 turn. One of my keys/tabs was broken off and the switch was not fully seated. Ever notice, while using cruise control, you can hit the brake ever so slightly and it will disengage but the brake lights do not come on? The cruise circuit opens a fraction of an inch (in range of motion) before the brake light circuit comes on. Just ordered a new switch.


Also, for those of you wanting to test your servo. Below is a pic of the servo. If you put +12 to pin 3 and ground to pin 4, you should hear a slight click. While you still have voltage applied, also ground pin 1 and then pin 2, separately, you should also hear more clicks as these activate. This is telling me that at least, electrically, my servo is working.

 

Well, I am still waiting on the switches from the schmuck on ebay (don't ask!). With the new brake switch in though, it is working fine. This doesn't make sense from an electrical point of view, the power just goes through the switch to the speed servo and only serves to disengage it, not shut it completely down. The only thing I can figure is that somehow the PCM is thinking that the brake is staying on too long, therefore shutting the cruise off completely. When you replace the brake switch, it helps to have the switch warmed to about 80*. Those little ears that hold the switch in are pretty delicate and they need to flex a little when fitting into the bracket. I will still post up correct resistance values (as compared to the service manual) when I finally do get them.

 

Okay, so not sure what has changed between my '99 and the '01 service manual but my resistance (ohms) values are consistent across the original set of cruise switches and the used set that I just received. My values are as follows:
"on" =460
"set" =4300 (4.3k)
"cancel" =1200 (1.2k)
"accel" =15,400 (15.4k)
"coast" =3000 (3.0k)
According to the table below, the "accel" and "coast" are spot-on or close enough. The others are wacky. But, after I replaced the brake switch, my cruise is working normally, so I am posting these values as reference. The table below is from the '01 service manual.

 

Wonder if you have a dirty connection somewhere...... Although, if everything works as it should....... Well, wouldn't be the first time misinformation was printed in the service manual......

 

All of my connections were clean and solid. The resistance values are/were measured right at the switches. And both being about the same? I'll go with mis-info. Just got grins, I even tried with them in-circuit, to see if that affected the values. Nope.