Recently my 2003 XKR message center has intermittently been displaying the Cruise Control Unavailable / Check Rear Lights messages. The rear lights all work but the cruise control typically did not work. Sometimes the cruise would not work even when I was not receiving the message. I was not able to find too much in the forums about this so I thought I would write up my results.

On my car the culprit was the brake light switch which is mounted above the brake pedal. The switch has two sets of contacts, one set is open when the pedal is not pressed and the other set is closed. The open contacts close when you press the brake and this activates the stop light relay which in turn operates the rear brake lights. The closed contacts open when you press the brake pedal and this signals the cruise control to cancel. The state of these two switches is monitored and if they are both on or both off at the same time, this indicates a fault thereby generating the message. Since my stop lights always work, I checked the normally closed switch contacts with an ohm meter (center two wires in the connector). With the brake pedal in the resting position I expected to see less than one ohm resistance. Instead, I saw a varying resistance and could only obtain less than one ohm when I pulled the brake pedal up from the floor. Next, I connected a 12 volt bulb between pin 2 and ground (key on). The bulb was lit steadily and turned off when the brake pedal was depressed, exactly as it should operate. This indicated that the switch contacts were probably dirty. I saw in the forum that some have disassembled this switch and cleaned the contacts, but the switch looked too hard to remove. The past few days I have driven the car and the problems have disappeared, so I think the solution may be to connect a resistor between Pin 2 (blue wire) and ground so that there is more wetting current across the contacts. I plan to wait and see how long it takes for the problem to reoccur before I do anything else.

If anyone else has this problem, I would first connect a 12 volt bulb (old tail light bulb etc) between pin 2 of the switch and ground with the ignition switch on and verify that the light is on steady when the brake pedal is at rest and off when depressed. Cycling the switch with the current drawn by the bulb appears to break down the nonconductive film on the switch contacts.

 

Thank you, solutions to problems are always GREAT to hear!
Brian

 

Very good addition ajsva!

 

I had just bought my Cat thursday, 2003 XK8, and the last leg was getting dark .. and I see this neat little screen now .. giving me the same exact message as you described. I wasn't using cruise, but I surely needed my rear lights. My partner stopped for gas, so I got out and checked .. all the lights were working fine ... whew.

Thanks a million for posting this. Mabe a Mod could start a Sticky for Error Codes, or even better, devide the board up into subsections according to subjects. I am a newbe here ... but works well on the Ford Truck big board, and doubtless this site will surely grow as more Jag's come out of lease and into private hands. For me, the closest Jag mechanic is two hours south, so this is an incredible resource.

 

Have you seen our FAQ page for the XK section attaboy? All sections have one, but the xk8/r is my pet project after several of our members compiled the original topics and links, and I'm always grabbing good subjects/threads to add to the list. If I miss one (its not on there) feel free to send me a PM or report to a Moderator, and I'll get the notification.

 

I just fixed mine, but I'm too cheap to spend $70 on a switch assembly. I ohmed out the two microswitches and discovered that the N/O and N/C contacts on the brake light switch were both working properly, and the N/O contacts on the cruise switch were working, but the N/C contacts on the cruise switch were not. So, I unsoldered the two microswitches from the little circuit board, swapped them, and resoldered them. I ohmed then out, at the pins to the connector, and both switches were doing what the needed to do (the N/C contacts on the brake switch aren't used, so it doesn't make any difference that they don't work). Reinstalling the assembly back into the car was a royal PITA, but I got it done eventually.

 

Kudos to you!

 

You and testpoint are competing for the 'tightwad' title?

 

Thanks for a great post! This MAY be what is wrong with my car. I am going to have my mechanic look into it.

 

Thank you for this useful information. I am having a problem with being unable to move the lever from park. I had thought it was the brake light switch, but the lights still work - and I have to use a screwdriver down the hole next to the gear lever (which is closed with a torx bolt) to release the gear lever.

I have now experienced this additional cruise control message - so the answer certainly seems to lie in the brake switch. The car is still under guarantee (bought second hand from a jaguar independent garage) and they'll replace the switch next wee.

 

Really? How often do you go? I go several times per day, so if it was my car they'd be replacing the switch TODAY.

 

Thanks, Reverend Sam!. I suppose I could go to church for this, but then I would have to wait until next yea.