2003 Jaguar Xj8; 120,000 miles

Intermittent lack of cruise control, failsafe engine mode message not on.
After trying for cruise control enough, the failsafe engine mode message will appear and cruise control will be completely gone.
No DTCs and the message disappears when the car is restarted.
Brake lights turn on and off as expected.

I believe this is a faulty brake switch, but someone please confirm my diagnosis.
Also, is there a way to test the brake switch with a multimeter before I aim the parts cannon at a potentially innocent component.

 

The two circuits in the brake switch are the outer pins for one circuit and the inner pins for the other. Check the continuity with the pedal relaxed and then depressd.

 

Thank you.

 

Hook up an OBD analyser/scanner. There is a specific code for this problem.

Jeroen

 

There were no codes. . .
Do you need a special kind of scanner to read chassis codes as opposed to just engine codes?

 

Don't trust just using a multimeter on the brake light switch. Mine tested fine, but replacement cured the car dropping into failsafe mode & disabling the throttle when the cruise control was 'armed'.

I saw a thread on here recently that said resoldering the microswitches to the board in the switch normally fixes the issue. I've not tried it on mine, but will as I kept the old switch because I couldn't prove a fault on it with my meter.

 

If you do a search you will find the part# for the microswitches.

 

I have found that thread (thank you) and ordered the micro-switches. I will do a write-up once they arrive.