pineapple_tree

Exactly as the title states, my cruise doesn’t work unless i’m holding down the “set/decel” button. If I let off the button, it stops cruising and I slow down. I’m pretty sure it’s an issue with the switch, but I’d like other opinions.

My cruise works wonderfully when I hold that button down, no issues whatsoever from it working.

pineapple_tree

Anyone? I tired a new switch panel and it does the exact same thing. So there’s something i’m missing here. The servo is installed correctly, so is the clockspring and buttons. When I press the brake, it disengages cruise when i’m holding down the button. But as soon as I let off the button, it slows down.

I’ve read through the FSM, checked everything that I could, and still it only works when I hold down the set/decel button

pineapple_tree

Well I found this online:

How true is this? Do I really need a PCM that’s for an automatic 2.5?

pineapple_tree

Here’s some more insight on this issue…

If I’m on the highway, and I let off the button, I can actually feel the cruise control try and grab but fail, and it does it in 2 second cycles. If I brake, then it stops completely. So this tells me that either the PCM is having trouble remembering what the speed it because it won’t work with the button and try to make it work but fails when I let off it after holding it for 20+ minutes, or the servo is going bad. I’ll have a look at my FSM and see how to test the servo.

It’s just confusing since it works absolutely fine when I hold the button down, but won’t work when i’m not pressing it.

Oh, also, if I push “resume”, it won’t resume, even if I let off the button and immediately press “resume”.

lawsoncl

Have you confirmed that the switch and clockspring are good? FSM should have the resistance values to test the switch (it changes the resistance depending on which button you're pressing).

exasemech

I thought your vehicle was a manual? The article says the. PCM must match the transmission type. why would you want one for an automatic?

Is your PCM the original or has it been swapped out at some point?

pineapple_tree

I had a look in the FSM and there wasn’t any mention of resistance values, just whether or not there was continuity or not between the different pins. I have tried 3 different switches, and they all work the same way. I didn’t see anything for testing the clockspring, but i’ll still look and see if I can find anything.

pineapple_tree

My PCM has been swapped out once before. It has a sticker on it that says something about lifetime warranty and don’t remove the sticker type deal. There was some mention of testing the pins going into the PCM for different voltages that i’ve yet to try, but it says if you want to really test the cruise system, you need a scanner.

There’s a few other things I still need to try from the FSM, and eventually i’ll get to it. I just can’t find any info on this at all, aside from that one forum post I took a screenshot of. It’s the only thing in existence that describes the same issue as me, but only on a 91 which has the turn signal stalk cruise

lawsoncl

Erm, I don't remember now. Is the 1995 cruise switch on the steering wheel or a separate stalk? I thought it was the buttons on the steering wheel that did the changing resistance, and the stalk had dedicated wires for each switch.

If it's a manual PCM, it might be looking for a clutch switch, and you just need to figure out which pins to connect?

pineapple_tree

Okay. That makes sense. I’m guessing the PO either bypassed the clutch switch or deleted it, since I can start my Jeep without holding the clutch down. Maybe the PCM is thinking that the clutch is continually being pressed down, so it won’t engage cruise control unless i’m holding the button down?

I don’t know. I’ll look at some wiring diagrams to see what wires are for the clutch switch and wire it back up and see if this fixes this issue.

And on a 95, the buttons are on the steering wheel at the bottom. The PCM just reads the resistance between the pins to determine which switch is pressed. The resistance values changed in 96 when they added a light to show that cruise was active, then they changed it more before 97 where they moved them to where the horns are.

exasemech

Don't assume your 95 had a clutch switch. My 96 4.0 manual xj that I bought new way back then didn't have one-but it also didn't have cruise control
Perhaps looking in at the owners manual or shop manual for your vehicle might be more useful than guessing.

pineapple_tree

I don’t think I had a clutch switch. There’s no mention of one anywhere in the FSM.

However, everything i’m reading is pointing towards a wiring issue. Maybe somethings crossed, maybe there’s a short somewhere, who knows. The FSM does tell me how to check everything, so on my lunch tomorrow i’ll try my best to test everything it tells me and see if I figure out anything

pineapple_tree

Well, I tested everything at the PCM side. Everything tested good, except for one part where I had to probe pin 50, and with the switch on or off, it should read 0 volts. When I press either the resume or set button, it should read battery voltage.

So, with the switch on, key on, I probe pin 50, press the resume button, it shows battery voltage. However, if I press the set button, it does not show battery voltage. I tested the switch, and everything checked out. There were other steps involved that required the “set” button, and it passed those, except for this step.

So, I think my issue is wiring related.

lawsoncl

Looking the wiring schematic, I don't think that's true. Looks like pin 50 it should only have voltage when you press resume. Pin 48 should have voltage when you press set. The continuity test listed in section 8H seems wrong to me.

pineapple_tree

Yeah. I’m thinking the same thing. That white/light green wire that comes off of pin 50 in that same diagram I looked at only lists as the resume sense, but section 8H says that at pin 50, it should only show battery voltage at that pin when either resume or set is pressed.

Im really at an even bigger loss now. The switch is good, the clockspring is good, because it sends information to the pins at the PCM, and the servo should be good, because those rarely go bad from what I hear. And even if it was bad, it still wouldn’t explain why I can use my cruise only when i’m holding the button down.

I also figured out that if I hold down the resume button while holding down the set button, it will accelerate like i’m mashing the throttle, but stops when I let off either button.

I also saw that the PCM was from 2007 ish, so it’s about 15 years old. Because if everything else is testing good, then it has to be the PCM right?