The image above is the switch on the brake pedal arm on a 2001 Jaguar XJ8 with 122,000 km on the clock. The car was intermittently showing the "FAILSAFE ENGINE MODE" message on the dash. Also, the cruise control would not function.

The switch is held in place by one bolt visible on the pedal arm, and the top slot fits into a pin on the arm. As the switches themselves appeared fine, and are normally very reliable, I looked for problems elsewhere.

The switch is actuated by a steel pin that is welded to the pedal arm. This pin pushes against the nylon cam at the area indicated by the red arrow. I noticed the nylon surface was slightly worn away where the pin had rubbed on it. You can see this wear in the photo - the nylon is a bit "dished".

I cut a suitably sized piece off an unwanted credit card and epoxied it to the nylon at the location shown by the arrow. Problem solved. No more messages! Cruise control operational as normal.