I know I'm going to be toasted for this, and I DID try the search.
As of yesterday, my cruise function won't engage. Started by working intermitantly, then finally, nothing. Tried turning off/on (by the lever) tried disconnection of battery, checked the fuse, finally took to my indie shop. They said the PCM is likely to be the problem. The XFire only has 26,XXX miles on her, she's an '07, 6 speed.
Any ideas, Please!

 

Anytime a problem occurs on a car, I reach for the OBD reader and search for fault codes. Having said that, I have had cruise control fail on other makes/models and it was nothing more then a vacuum leak in one of the hoses that control the cruise function. I have no idea if the Crossfire uses vacuum to control the speed however.

 

Thanks Tony, the indie shop did the reader and sure enough, no codes. That's when he said to try a dealership. They are "going to call me this morning" after the Tech gets in and looks her over. We'll see.

 

I have this vague memory that you once said you shift your manual sometimes when in cruise control....wonder if that might have affected it? Can't imagine why it would.....but most people with sticks probably don't.......

 

The car will re-engage the cruise control once the clutch is released, provided the computer doesn't sense an over-rev. I'm pretty sure this is in the manual. There's no problem with shifting when the cruise control is engaged as long as you don't go from 6th to 2nd or something along those lines of ridiculousness.

As for what the cruise control uses to operate, our cars are drive-by-wire and assuming everything else (which is probably the case) is electrically controlled, then the cruise control modifies throttle input electronically.

 

I'm not a mechanic, but would have to agree on the theory of the drive by wire method of controling the cruise. It does say in the manual about up/down shifting with the cruise engaged, but shifting must take place under 4 sec. Supprised me the first time it stayed on after shifting, then looked it up in the book.
Thanks for all the inputs, still waiting for my "morning call".

 

From the shop manual.

Note: A cable and a vacuum controlled servo are not

used. This is a servo-less system.

Control of the speed control system is accomplished by a
speed control switch (1) which is located just above the multifunction
switch (2). The speed control system also uses other
components of the vehicle to accomplish its tasks. The five
other major components used are as follows; The PCM, Accelerator
Pedal Position Sensor, Kickdown Simulator Switch,
Throttle Body and the Clutch Pedal Position Switch (Manual
Transmission). The speed control system is designed to operate

at speeds above 25 m.p.h. (40 km/h)

 

All those switches and sensors. Again, probably something electrical. The PCM is listed there... could be the problem.

 

Update, was told it's the switch at the base of the lever. $475!!!!! And that's if the "clock spring" doesn't go haywire during disassembly!!!!! REALLY!!!! Oy Vay!

 

That sucks, Terry! Well, nobody said this was going to be a cheap love affair...

 

Ain't THAT the truth!! Hey Jon, hope all is well with you and Sue.

 

Try a Mercedes part, it'll probably be half the cost.

 

Perhaps an electric switch cleaner safe for plastics?

 

After looking at the circuit diagram, I thought that the problem could possibly lie in the Clutch Pedal Position Switch. If this was faulty it would not let the Speed Control work. This must be a cheaper part.
It also may be getting a signal that the brake was applied, but I do not know where that switch fits in the system. If the brake lights were on all the time it would be simple to diagnose.

 

Just an update, it was the switch at the base of the lever. Total price from dealership (are you setting down?) .....$468.00!!!!
But, now she's back home in her garage where she belongs.

 

Dear god... I hope you didn't pay for that out of pocket.

 

Why, Yes I did. I bought this car used. As is warranty.