My 98 XK8 has recently begun displaying the Failsafe Mode indicator light on an infrequent basis. When it happens the cruise control shuts down, but the car continues to run without any change. I had always heard that when the light came on it would force a reduction in speed, which has not been the case.

Any suggestions on what might cause my Failsafe activation?

 

That seems to be often caused by the brake switch just behind the pedal, on those cars. There's a few threads about that on here.

 

You need to read your OBDII codes, otherwise you are just guessing. Buy a reader or get it read for free at Autozone or Advance Auto Parts.

 

Does it only go into Failsafe mode when using cruise control, ie after setting the speed in cruise? is your car a pre 2000 model with vacuum controlled cruise ? if so I had the same problem which after brake switch tests turned out to be a leaky vacuum hose located under the wing adjacent to the vac solenoids that control the cruise speed.

trace the vacuum hose from the throttle body and follow it to the vac accumulators and solenoid valves, and then to the vac source at the rear of the engine. Look for cracks, splits, loose connections etc. mine was a small split at the end of a hose. After fixing that, cruise works 100% and no more failsafe mode.

 

It appears to only take place after I have turned on the cruise. The car is a 98. I intend to check the lines today.

 

WhiteXKR - sometimes we tend to overlook the obvious, which is what I have done. Spuddyo suggested looking at the vacum lines which I plan on doing today. I am also going to have Autozone read that code for me. Thank you.

 

Did you find the problem ?

 

spuddyo, it's never come on again. I've tried to duplicate the issue to no avail.

Thanks for your concern and recommendations.