'99 XJ, swapped in a cruise control system, worked perfectly for several weeks. This weekend, it just stopped working as if a fuse blew or ??? No more dash indicator, no more anything. Everything else seems to work just fine still, no airbag light or anything like that and the horn still works. Is there a troubleshooting guide for this anywhere? I've read a TON of threads on cruise control issues, but very few end up with resolution...

 

Vacuum? Retrace all the wiring you did.

 

I do need to check the vacuum, as I also had an intermittent high idle problem throughout the day yesterday... but my question with that is, if vacuum fails, does it prevent the dash indicator from illuminting? I would think that the system would at least "energize" when you hit the ON button, but obviously fail to hold speed or engage at all without vacuum...

 

OK, I pulled a DTC from the system: P0123, which equates to a high TPS voltage issue. The CEL was on for a couple of hours during the high-idle problems, but both the high idle and the CEL have gone away? Is there ANY possible relation between a TPS problem and my cruise control dying???

 

I've done a lot of reading today on P0123 codes and cruise control issues, and a vast majority of them seem related by a common failure: the clockspring. My AIRBAG light is not illuminated, and my horn functions normally, but my cruise will not turn on at all. I found a great write-up here:

http://www.batauto.com/articles/AT/V...xplained.shtml

I have not had time to backprobe the PCM harness as he did in the article, but what I did do was pull the horn relay - no luck. Next I replaced the relay and tried engaging the cruise when blaring the horn - no luck. If I'm reading the article correctly, this tells me the same thing: my clockspring has given up on me. Can anyone verify if I'm thinking correctly here? The only other thing I can think of is if perhaps the switch itself went bad... Is there a way to test this without tearing the wheel apart again?