I have a 1999 XK8 with 100,340 miles. I recently had a misfire code repaired with new plugs and new coils for cylinders 4 & 8. I now have a new yellow warning light and a Failsafe Mode message which comes on after driving a few miles. The only driving issue I notice is cruise control doesn't work when it's on. What are the likely causes. Thank you for any advice.

 

can you pull codes?

Anyone that owns these cars that have a Droid phone should DL the Torque Pro app (3.99?) from the app store then buy the ELM blue tooth adapter off of EBAY, as much as we all get codes it should be something to be carried in the glove box.

 

One possibility is the brake light switch. It has two switches, one to turn the lights on, the other to disable cruise control. Search the forum for DIY replacement.
There could be a problem with a wheel speed sensor or cable, but that should cause the ABS light to come on.
If there is a indy shop in your area that has software for Jags it might be worth the expense to have them check for codes, but I would stay away from dealers as they will likely tell you half the cars electronics must be replaced at a astronomical cost

 

Dose torque pro read C codes? I thought that would only read P codes.

 

I had this with broken motor mount. As soon as cruise tried to increase speed this occurred (failsafe mode, cruise stops,cruise lights out).

It was the disconected vacuum line to the throttle body (motor movement=pull on vac hose). So just in case=same, I wanted to let you know. Good luck with it.