Backstory:

Purchased my '03 Ram 2500 about a month ago. It was pretty base model except for the upgrades the previous owner installed, all of which are non-oem. One of the first things I noticed about the truck was it didn't have cruise control. So, naturally I looked around and found that all I really needed to do to install it was purchase the OEM switches. So I did. Excitedly I installed them to find that cruise still didn't work.

I then saw reports of having to reprogram the PCM so it knows it has cruise control. Called the dealer and they confirmed that is the case sometimes. So I took it in and they agreed to perform the service for a modest $80.

After a bit they told me that the option to enable cruise was not on the DRBIII menu at all. They know where to find it on the Starscan but my model year is not can-bus so it won't work. Finally another mechanic mentioned that on the 03's that the step of reprogramming isn't required, so something else is wrong.

Current issue:

Today I took the switches out and decided to test them with a multimeter. I guessed that the center pin on the pigtail was ground and that seems correct as when I tested the left hand (on/off) switch with the buttons pressed, I got resistance values.

On the right hand switch (with 3 buttons respectively) I was unable to get any resistance values unless all three buttons were pressed simultaneously. Tested the voltage on the harness in the steering wheel and all the lines tested at 4.8V so there is power.

So, the question: Is my testing valid on the switches, or is the absence of resistance values on the RH switch normal? Do I have a defective switch? If the RH switch was defective would that cause the cruise light to not engage even when the on-off switch is pressed? Or is it possibly something else entirely?

 

Search for any post by weedahoe and in his signature he has the links to the service manuals and part catalogs, that will help you out with the proper testing of the switch. My 02 is a can-bus system (I think 02-05 is all can-bus, and 06+ is TIPM), so I'm not sure what your dealership was talking about, but the idea that the PCM needing to be re-programmed does sound valid.
Mine came with cruise control and I hate it, if I set it to 65 and when the truck feels the need to accelerate to maintain the speed, it will actually surge past 65 and not let up until it hits 70.

 

Thanks for the reply

I want the cruise control mainly because I find that with the size of the vehicle I have trouble maintaining a consistent speed on long highway trips especially on slight grades. Cruise just makes it easier for me I suppose.

As far as the computer, there was another dealership that I talked to that seemed to know exactly what I was talking about when I asked so maybe I'll head over there and see if they can get it working. They were about $25 more expensive than the one I went to but maybe that's what I need.

First I'm going to check out the service manual to see if there are testing procedures for the cruise switches. If it's just a defective switch I can live with that. It's under warranty.

 

Good luck!

 

Well, I just mulled over the schematic diagram and after understanding how it's wired, tested the switches properly, and they both appear functional.

Kinda at a loss. I'll talk to the dealership again and see what else they can try.

 

this could be a stupid suggestion, and i apologize if it is, but you aren't missing something simple like adding a fuse into the correct spot in the fuse box are you?

 

Not a stupid suggestion, I'm taking anything...

I did check just now. I had looked at the fuse box before to see what fuses are there and I see no fuse dedicated to the cruise control system. Also, all fuse spots are populated (even things like heated seats, power pedals, etc that I don't have) so if it is a fuse problem, it's a blown fuse rather than a missing fuse. And since there isn't one specific to cruise, I would assume there would be other non-working systems that would tip me off. So, in my opinion it's not a fuse. But I appreciate the suggestion.

I do notice that the "cruise" light in the dash lights up momentarily as the system boots up, but I can't remember if it has done that all along or not.

 

Its possible that the necessary wiring is missing from the PCM harness from the factory. Study your available schematics carefully and trace your wiring.

 

Never tried to add cruise on a truck that didnt have it so I dont think I can help much but as mentioned above, feel free to click on the links in my sig for the service manuals

 

@Lifttruck
I believe the wiring is all there, it's just 3 wires to the PCM, and according to the meter based on the schematics the two signal wires have voltage on them and the 3rd wire (sensor ground) is connected as well.
@weedahoe
Got the manuals from the links you provided. Thank you.