Car has been sitting for a week in 5-25 degree weather in a garage. Fired it up and let it run for a minute. Drove it for about 10 min then got a Yellow Cruise Control not avail message/light. No other warnings. Got to work, shut it off and then back on, hit the brakes a few times, rev backwards then pulled forward again hitting the brakes. Did not come back on. I think I can chalk this one up to the battery prob is weak. Last time I checked it was a hair below spec to be a good battery. Last week I just recalled, that I had to reset the passenger window. Maybe time for a new battery or drive it more or put a trickle charger on it if I am letting it sit.

 

In that weather I definitely recommend a trickle charger. I don't know what is automatically heated in the Jag but had a BMW and the wing mirrors auto-defrosted and killed a good battery in 3-4 days. I finally had to put a battery switch on it to kill the power when it was stored for the winter. That and a trickle charger allowed me to use a battery for 6 years

 

also the brake switch in the car is a common problem disabling cruise control

 

Hate to say it, but that is how my own brake switch failure made itself known. For a while, the no cruise control message was intermittent. I could drive for an hour with no message, then it would appear. It also said check lights, but my brakes lights worked. So I ignored the messages for a while. Then, without my knowing it, my brake light stopped working. I found out when one day I suddenly slowed from about 50 to about 15 to make a sharp right corner, and the car coming up at 50 behind me, leaned on his horn as he changed lanes and blew by me. Realized he was possibly pissed because he saw no brake light to warn him as I suddenly slowed for the turn. Checked and sure enough, no brake light. It was obvious the switch had failed. When I removed it, I found the spring tabs on both internal switches were broken off. I guess the cruise switch went first followed shortly by the actual brake light switch. New switch, all better. There are any number of r&r procedure threads. Pick the one that sounds easiest to you.

 

I just noticed that my brake lights on my 2003 xk8 only work with the ignition switch turned on. Is this normal? I had a rear light message some time back and ended up replacing the brake pedal switch. However today I noticed that my cruise control does not function at all. No warning message about cruise control or rear lights. All lights function if ignition is turned on. But depressing the brake pedal with car turned off there are no brake lights. Any thoughts? Also today I got a message that the hood was not latched. Pulled over, opened hood and re-closed it. Still had message. Turned off car, restarted and hood message went away. Battery is almost 4 years old. I only drive "Mick" (Jaguar) on the weekends or to go and get ice cream. By the way, I didn't name him, my wife did.

 

probably time for a new battery or a trickle charger also try locking the car with the remote when not in use it allows the electrical system to go into sleep mode quicker.

 

Thanks wolfpk1. I always lock the car with the remote, even in the garage. I always keep the jag in the garage anyway. Any thoughts about the brake lights not coming on when the brake pedal is depressed but the ignition is switched off? My recollection is that the brake lights should come on when the brake pedal is depressed, no matter what. Also, the car starts right up, no difficulty.

 

After reading your post I decided to try mine. They do not light up with the ignition off.

 

mine don't light up with ign off.

 

Mine do not light up either; nor do the brake lights on my Mercedes unless the key is in, and turned to position I.

 

Noob here. My first code was the "Check Rear Lights" code. My Jag didn't come with a mechanic in the trunk, so I was thankful for this tread. Looks like the Brake Light Switch is the culprit. Much appreciated.

 

I just recently bought a 04 XK8 convert and had CEL problem right off. Had a clogged fuel filter and a vacuum leak. Those were fixed as of this morning and it runs fine. However, I ordered a horrendously expensive brake light switch also because the "check rear lights" and "cruise control unavailable" messages were frequently on. But after fixing the other problems, I noticed the cruise message has stayed off and cruise works fine. I know it's not related to the lean CEL issues but any comments would be interesting. I did look under the dash with a mirror dreaming about the upcoming task of changing the switch and did reach up there and feel around for a minute but that's all. Thoughts?

 

The brake pedal switch assembly can get quite finicky after a few years. You probably experienced an intermittent failure, and that is likely to begin occurring more frequently. The best repair approach is to replace the two flaky microswitches inside the assembly with better ones. That requires some soldering skills....

 

Me either no light if the switch is OFF