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Cruise control- 2000 XJ- shuts itself off

D

DPG

NAXJA Forum User
Location
Kansas
Yes, I've searched and can't seem to find what I need.

My cruise on my 2000 XJ works fine when it works. No surging or vacuum related issues. This is electronic.
Usually 5-15 minutes working and then it shuts itself off. The green light on the dash goes off and that's it. It acts just like it would if you hit the off switch.

Once it shuts off, it will NOT come back on again until I have shut the engine off and restarted it. Often, it won't come on at all and it's working less and less lately. Degrading...? More often than not, it won't come on at all now, but once in a while it does...

I have replaced the underhood whatchamacallit- solenoid or actuator or whatever. (Can't remember right now) I have also replaced the on/off switch in the steering wheel. Haven't replaced the right side accell/decell switch.

Can the clockspring be causing this? The horn always seems to work fine, but a jeep tech told me that clocksprings can work intermittently. I thought the clockspring either worked or it didn't, but...?

This silly thing is driving me nuts, so any help would be appreciated!

Thanks!
Dirk
 
DPG said:
Can the clockspring be causing this? The horn always seems to work fine, but a jeep tech told me that clocksprings can work intermittently. I thought the clockspring either worked or it didn't, but...?
Click to expand...

I just replaced the airbag clock spring on my 98 cause the horn and the cruise control weren't working. But they were not working at all. I haven't heard anything about them working intermittently:huh:? Have you checked the fuse? I'd do somemore research on it before I went out and bought a new clock spring, they are pretty pricey.
 
I don't know of a fuse for the cruise...? Nonetheless, if a fuse was blown, that would tend to be a on or off thing too.

I don't want to buy a clockspring either. I was surprised that he told me that could be it.

Might have to take it to a good automotive electric guy. Just hoping someone here has run into this issue.
 
DPG said:
I don't know of a fuse for the cruise...? Nonetheless, if a fuse was blown, that would tend to be a on or off thing too.

I don't want to buy a clockspring either. I was surprised that he told me that could be it.

Might have to take it to a good automotive electric guy. Just hoping someone here has run into this issue.
Click to expand...

The brake lamp switch attached to the brake pedal has often been found to be either out of adjustment or faulty, causing cruise control problems. I would look into this before changing a clock spring.
 
There is no fuse.

97 and up had what appears to be a circuit breaker built into the PCM. My 98 would arm but not drive the servo. I found that the voltage from the PCM would drop out with the brake light switch in it's "normal" (brakes off) position and would stay on with the barkes applied. Tested with the switch out and on the driveway. I replaced the wire from the brake light switch to the servo and the problem went away. Evidently there was a short in the harness and the PCM would trip. The only way I had to reset it was to cycle power to the PCM i.e. shut off and restart the engine.

Dirk, it almost sounds like there is a problem with the switches on the steering wheel. The pcm uses a multiplexed resistance strategy to figure out what you are telling it to do. Perhaps the OFF switch is failing.

In my case, the CC light on the dash would remain lit but the voltage dropped out. Your case sounds like the CC is being told to shut down. I would swap out the switch with a known good one.

Switch Compatability:
97 and 98 interchange
99 to 01 interchange

Differences lie in the resistance. The PCMs are rather picky about what they want.

Just my .02...
 
Interesting. Sounds like a wiring harness issue or the brake light switch to me.

Never knew there was a circuit breaker in the PCM for the cruise solenoids... very interesting.
 
Thanks! That gives me some new stuff to check.

OGS: I did replace the on/off switch in the steering wheel with a brand new one from the dealer. Nothing changed. I guess anythings possible, but that sure makes me want to eliminate that switch as being the problem...

Any chance it's the other switch on the right?

I don't know about the brake switch, but it will shut off without using the brakes at all or hitting a bump or anything.
I can be cruising along on smooth open highway and the dash light will suddenly go off and the cruise is gone...

Thanks again!
 
o-gauge-steamer said:
Evidently there was a short in the harness and the PCM would trip. The only way I had to reset it was to cycle power to the PCM i.e. shut off and restart the engine.

Dirk, it almost sounds like there is a problem with the switches on the steering wheel. The pcm uses a multiplexed resistance strategy to figure out what you are telling it to do. Perhaps the OFF switch is failing.

In my case, the CC light on the dash would remain lit but the voltage dropped out. Your case sounds like the CC is being told to shut down. I would swap out the switch with a known good one.

Switch Compatability:
97 and 98 interchange
99 to 01 interchange

Differences lie in the resistance. The PCMs are rather picky about what they want.

Just my .02...
Click to expand...

That's the strange part- Mine won't always come on after I've started the jeep, but once it goes off it will definitely never come on again til the jeep has been restarted...
 
kastein said:
Interesting. Sounds like a wiring harness issue or the brake light switch to me.

Never knew there was a circuit breaker in the PCM for the cruise solenoids... very interesting.
Click to expand...


This is an assumption on my part. The way it operates leads me to believe this to be the case. I am more than happy to be corected as this is how we all learn.

The brake light switch will shut down the servo, but will not (on my 98 anyway) shut down the entire CC. I only need to tap the resume function and off it goes. Dirk's is getting shut completely off as witnessed by the dash light extinguishing. Given the general shady quality of our wiring, you are probaly correct and this could be a wiring gremlin.
 
Probably way off base, but on my 95 a vacuum hose leak along the firewall was the culprit. Easy to diagnose since HVAC flap (I think) controls won't work either.
 
The big kicker here is that the CC light goes off. If the vacuum was low, the servo would not operate but the light will stay on until the system is shut down. I belive that you only need 10"Hg for the CC

Possible bad PCM? Electrical at any rate, sounds thermal. Do you have acces to another PCM to swap? Can be had at the JYs. If it works, the dealer can reflash the VIN into it to make the Emission Nazis happy.
 
o-gauge-steamer said:
The big kicker here is that the CC light goes off. If the vacuum was low, the servo would not operate but the light will stay on until the system is shut down. I belive that you only need 10"Hg for the CC

Possible bad PCM? Electrical at any rate, sounds thermal. Do you have acces to another PCM to swap? Can be had at the JYs. If it works, the dealer can reflash the VIN into it to make the Emission Nazis happy.
Click to expand...
That's what has me scratching my head also. IIRC (my cruise hasn't worked in a while on the 98 due to a super gummy switch panel I haven't felt like messing with yet) the cruise light stays on when you cancel cruise using the brakes. I could swear the only way for the cruise light to turn off is if you shut the vehicle off or use the cruise on/off switch.

Unless I'm remembering wrong and the cruise light goes off when you cancel cruise with the brakes, this points at a wiring harness fault between the cruise switches and the ECU, or an ECU fault. I can't think of anything else that would cause it.
 
Interesting development. On one of the times that my cruise was working, I hit the Cancel button to shut it off but the cruise would not disengage.
Had to hit the brake to disengage the cruise.

Also, I had previously replaced the ON/OFF switch on the left side, but I wasn't aware that they are different for specific years. I might have gotten the wrong one...

Going to replace both switches soon and see what happens from there...
 
Well, I've replaced BOTH of the switches now for a second time. (Also previously replaced the servo)

Funny- If I can get the power light to come on, often the same switch will not activate or set the cruise speed. I may have to hit the switch multiple times before it will lock in my cruise speed.

Then, hitting "Cancel" on the other switch will not turn the cruise off either. I have to hit the brake to get the cruise to release that speed. All this while the dash light is on...

Pretty soon, the light will just go off again on it's own and I can't turn it back on unless I restart the jeep. Even then, it's turning on less and less often...

Obviously, there's some type of resistance or short or something between the switches and the brains of this thing. Only works intermittently at best...
 
Dirk,
Do you have a FSM on the Heep? If so look up the two pins in the PCM and read the resistance ot the switches as they are pressed. Compare those reading to what they read at the clock spring connection and that will give you an idea of the state of the wiring including the clock spring. You could break it down further and meaure at the output end of the clock spring in order to isolate that component from the wiring to the PCM. Hate to say it may be the PCM...

If you do not have a FSM, let me know and I'll look it up in the one I have for my 98. I would suspect those connections are the same.
 
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