1998 XK8 Runs great- no other problems but when I engage cruise the fault light goes on and cruise shuts down. When I restart all is fine, no light but when I engage the cruise, it triggers the fault light. It never goes into limp mode. I disconnected the battery to no avail.
It may be my imagination, but it seems that I hear the throttle louder inside the vehicle than before the mode light strart coming on.
A large truck blew a tire and all the pieces flew under the Jag. Could I have picked up a small piece and sucked into the throttle body?
All the troubles seemed to have started right after that.
The car has only 40,000 miles.
ODB 11 shows no faults?

Help

 

Gary, I would be venturing to guess you have a problem with your throttlebody. This is a common problem with our cars. Granted, it could be possible that you have a wheel speed sensor that isn't working properly due to the tire pieces going under the car. That could also cause the cruise to not play right. If you need some pointers on how to check the speed sensors, let me know. But, odds are, if you remove the tires, you will see the wires hanging down and it will be obvious if you have a problem with that sensor or not (ie, wires will be damaged).

 

Thanks; Too frigid to work on it, but will check and clean T/B when it warms up.
What is a wheel speed sensor?? What does it do??
Gary

 

It is a sensor that senses the wheel speed.

Cog like disk behind the brake rotor magnetically generates a pulse in the sensor and is sent to the ABS/traction control unit. The control unit measures the speed of each wheel many times a second to implement the programmed actions of braking and traction.

 

How do you check the Wheel Sensors?

 

You don't check them as much as you clean the sensor and the cogged disk. Also check that the wiring is in place and not binding when the wheel is turned lock to lock.

 

There is a "T" vacuum fitting under the hood to the RH side of the throttle body. Check to see if it is broken and report back. You may need to remove the intake snorkle to see it.

May also have a brake switch fault stored that your scanner is not picking up (P1571), but check that fitting 1st.

 

Thanks--Thats exactly what it was. Broken T vacuum valve. Cost 1.00 to fix..

 

Glad I was actually able to help you.