I have the "cruise control unavailable" message, and I understand that the adaptive cruise control module is prone to internal corrosion. My 2004 XJR has 55k miles on it and the module looks extremely clean and totally uncorroded on the outside. SDD only suggests module blockage or failure.

1) Does anyone have experience of adaptive cruise control modules that look great on the outside, but are corroded to failure on the inside?
2) Is there a way to test the module it's self without taking it apart.

Thanks all.

 

The adaptive cruise system relies on the brake switch CONSTANTLY being de-activated in order to work properly. My car occasionally gives the "Cruise Unavailable" message and I have found if I furiously kick the trim panel above the brake switch under the dash it fixes it...for a while. It seems that if the switch is slightly wonky and gives an intermittent signal, the cruise system throws a fit and shuts down. One day I will get around to replacing the switch. I would look into this as the culprit before I start ripping into the module.

Good Luck
Jeff

 

Thanks Jeff. I went ahead and ordered a new switch from Amazon for $15. Hoping 3M5T-9C872-AB is the correct one. My brake lights are working fine and SDD is not telling me about any switch problems. Assuming the same for you? Won't be able to change the switch for a while as we are snowbirding after Christmas. No fun working under the dash, but definitely better than trying to fix a module that ain't broke.

 

Sounds like a good place to start
Switches will sometimes work.
When disconected then reconecetd again.