Hello,

This is my first technical question post to the forum. I have a 2004 XJ8 with standard cruise control and a non-turbocharged engine. The car has 100K miles on it. I have had the car less than one year. The cruise control is displaying some very strange behavior. Here are a few variations of the way it functions. I never know which one I am going to get.

Will not engage at all.
Engages and the + - buttons can't be used to adjust speed.
Engages and the + button works but the - button doesn't.
Engages but resumes previous speed instead of engaging at current speed (this happens without pressing the Resume button.)
The Resume button has not worked once since we got the car.
The Cancel button has not worked once since we got the car.

The most consistent way for me to get the cruise to work is to hold my speed for a few seconds, press cancel, and then press + at the same time as removing my foot from the accelerator.

The brake pedal always cancels the cruise like it should. I have had somebody follow me to verify that the brakes are not on when I am driving and the cruise will not engage.

Before I start replacing parts I wanted to get your opinions first. My first thought is that the cruise control button module is either worn out or dirty. I did perform several searches first before I posted and did not find anything like this.

I appreciate your input.

Bret

 

I don't recall seeing a similar problem posted but there have been some problems with

the wiring in stalks and the clock spring.

In case you don't know the clock spring provides a continous contact with steering wheel

buttons when the wheel is turned.

If it was my car I would:

Examine cruise buttons for good contact.

Examine wiring associated with above.

Clean clock spring.

 

It could indeed very well be a mechanical or wiring issue. But since the ACC is also part of the CAN bus system it could be electronic as well. If you have the possibility read the car for fault codes, it might help determining what's wrong.

Guus

 

I have not had time to look at the steering wheel switch or the clock spring. The good news is that the cruise is actually working just fine now. Every button is doing what it is supposed to do. The only recent difference is the type of driving we have done. Most of this car's 100K miles were highway miles. That tells me that the steering wheel has "lived" near the center for a long time. Recently we have been driving quite a few miles on roads with lots of tight turns. The only thing I can think is that the clock spring developed some sort of carbon buildup or film on or near the contact points from being in the same place most of the time. Is it possible that turning the wheel frequently on a few trips has somehow cleaned the contact points? It is the only thing I can posit. I might eventually take it apart to inspect it but for now I am going to leave it alone since every button is working correctly. Regards. Bret

 

Your theory sounds plausible and thanks for the feedback.

 

Well, I think my theory was incorrect. It is acting up again. Almost seems like the buttons are misaligned somehow. It isn't a huge issue so it isn't on my list of things to do right away. When I do get around to checking it out I will most certainly post my findings.

 

I have been getting an intermittant "Cruise Not Available" message when I start up the first time. If I try a re-start then I don't get the warning message. I'm thinking it may be a battery issue but my car starts up fine though. At this point I'm just in a monitoring mode since if I re-start my car everything works fine. At this point I'm marking this a peculiar Jaguar quirk.

 

My car has given the "cruise not available" a few
Times over the course of a weekend. It just so happened to be that the weather was torrential rains, so after a few days everything dried out and no errors since.

Any chance that this is related to heavy rain or car wash trips?

Thanks-
Mag

 

Yes cruise control uses data from ABS wheel speed sensors.

 

I was able to fix the cruise control tonight. When I thought about what could be wrong I had narrowed it down to the slip ring and the cruise control selector switch in the steering wheel. I bought a slip ring and a new switch assembly rather than hope it was one or the other and end up with the same problem. I replaced the slip ring since I had a new one but there was nothing to indicate that it was damaged. I replaced the switch assembly as well. There was definitely a difference in the feel of the switch assemblies. The old one felt mushy and the new one felt crisp. I took off for a test drive with my fingers crossed. I got on a long stretch of road without any stops and hit the + button and the cruise engaged! The + button responded with additional throttle and the - button backed it off. Cancel worked and resume worked. I was elated. The old button would work once in a while but really only to set the cruise. The resume, +, - and cancel would rarely do anything. So, long story short, I believe that the switch assembly was the culprit. I would have to put the old slip ring in to be sure but I really doubt that was part of the problem. Also, I was not getting any warning messages about the cruise control prior to this. That is why I deduced it was either the slip ring or the switch. Hope this is helpful to somebody with the same problem.