Ok if there is a solution to this already posted sorry in advance as I must have missed it. Cruise control on my 98 XK8 is not working, I have NO dtc's and i put the smoke machine on the vacuum lines today after confirming the 3 solenoids work ( who the **** decided to stick them in the wheel well! ) and the tanks held pressure. only hole I found was on the line from the TB to the solenoid assembly, which I fixed, but still no cruise control. any help would be fantastic...

 

My guess would be either your cruise control switch in the console is bad (stuck open), or the brake cancel switch on the brake pedal is bad (stuck open).

Does the red cruise control light on the switch work?

 

I agree with whiteXKR, usually (9 out of 10 times) if cruise control stops working as your first symptom, the brake pedal switch is at fault. one our popular members Reverend Sam actually starred in, and produced his own video showing how to replace it...just check the FAQ thread at the top of this sub-forum...and enjoy...you may need some more hands though, so enlist Jen or Neil, whichever one did not post the initial message.

 

Whitefly, the cruise switch is good, red light and all, was under the impression that the brake switches would throw a code if they failed...

 

I do not think that it would...I think that it is worth checking out.

 

Could a burnt out brake lamp cause this?

 

If the brake switch is bad, it should leave a message on the speedo saying "check rear lights, cruise not available". This happens to me sporadically, so I start the car and apply the brakes 40-50 times quickly and it goes away for a year or so. The microswitches get tired of being in the pressed postion after awhile. Exercising them gets them back in shape.
I suggest pulling codes to see if something is hiding in there. There is a cruise control module, check connections to it.

 

I just started getting the "check rear lights, cruise not available" occassionally. It always goes away when I restart the car. I'm gonna try oldmots' fix and see if it works.

 

+1 on the switch.

 

Morning H20boy, looked high and low for the video by the Reverend Sam including U-TUBE but no luck. Could point me in the right direction. I think it's this age thing.
George [0ap ]

 

Sorry george, I was mistaken on the 'video', there are pics and details in this thread that is a step-by-step process. Haven't done it myself, so it wasn't fresh in my mind what format the tutorial was in.

 

Thanks for that one h20boy
George

 

Ok here's an update, I tested the switches and they are both good, the cruise switch is good, now here is the really weird thing, on the way home thought I would try it out, it worked BUT I got no messages on the dash display, it sped up, it slowed down and for a few minutes I was a happy man! When I switched it off and tried again I got nothing and then a few minutes later I got an "engine in fail safe mode" message...it reset after I switched off the car but now I am really confused!

 

I am surprised that the brake switch was not the problem. I have not had the opportunity to check one to see what it does other than open/close. Do you know if the Throttle Body (TB) TSB has been complied with? I would also check and clean the TB plugs. I know that the TSB for the plugs do not apply for this MY but it would not hurt to check them.

 

If one of the two brake switches are bad it it will definitely give you a message on the dashboard display, so I don't think that's his problem.

I did replace my switch, and I did make a video. However, the video was so full of expletives, screw-ups, and busted knuckles that I decided it wasn't something I wanted to be associated with. It is locked in a high security vault with orders that it not be made public until 100 years after my death.

 

What you describe sure sounds like a brake pedal switch to me. It would likely set a code P1571. That's a corporate code that very few generic readers can read. I'm wondering if you just can't see it. The P1571 usually presents by making the Cruise Sw. LED go out, cruise stop working and an "Engine Failsafe Mode" message show up.

Just a thought............

 

I have a snap on MODIS at work, sadly with no jag software!.. On global obdII I can get some p codes, is there a way to trick the jag to talk domestic ford?.. I will research the TB tsb today.... Thanks by the way

 

The MODIS might work, if you had the Jag add-on; but there isn't any way to make the Ford equip work on Jag without switching it to Jag software entirely.

Good luck!

 

Hey Gus what is the number on the TB tsb?

 

It was a service action and I think it is #514 but it had expired. TSB 303-58 1999-2001 AJ-27 engines, Diagnostic Trouble Code (DTC) P0121 (Throttle Position Signal) may be present. A possible cause is a mismatch of electrical connector terminal materials between the Throttle Position Sensor (TPS) and the wiring harness electrical connector (gold terminals on the TPS and tin terminals on the wiring harness). TSB 303-52 1999-2000 xk & xj v8 Difficult or no-start/hesitation – normally aspirated AJ27 engines – Reflash ECM & TSB 303-35 1997-1999 xk & xj v8 Difficult or no-start/hesitation – normally aspirated engines – ECM flash reprogramming – service action s479

This reflashing can only be performed by a certified Jaguar shop and in most cases it is the dealership.