Regarding a 2001 XK8 coupe with 55k miles...

Last night while driving home, lights on and using cruise control...

(1) the cruise control went out (along with the red light near the shifter)

along with :

(2) a dashboard warning that said "Check rear lights/failsafe mode"

Neither thing has ever happened in all my Jag experience. When I got home, I checked the rear lights they were fine.

I shut off the car and checked the next day... the warning light was gone and the cruise control worked fine.

I have no clue as to what could have caused this, but I am about to drive down from upstate, NY to FL and was wondering if anyone thinks this could be the beginning of something bigger I should be concerned about before taking a long trip. Has anyone seen this issue before?

 

It is most likely the brake switch failing. There are two sets of contacts in the switch- one set disables the cruise control and the other turns on the brake lights. A common problem and plenty of information on replacement if you do a search.

 

RJ237 Thank you!

I will run a search for that on the forum... when the switch fails, do the brake lights go out altogether... last night that was one thing I was checking when the dash warning came on and the brake lights were working fine. And just a quick question as I don't have an owner's manual, is that brake switch easy to get at (hopefully).

Again thanks for the 411

 

as RJ said - plenty of info here on removal - check the stickies or do a search.


the brake switch replacement is easiest if the drivers seat is removed but it can be done with the seat in place - just takes a contortionist to do so!! It's a simple job - 2 bolts up in the engine bay and the electrical connection at the switch.


once I had the bad switch removed, I fed some fishing line down one of the holes and tied it to the new switch using that to pull the new switch into place

 

Here you go.

 

If you don't have time to address this before your trip, here are a couple of observations. I replaced mine just a year / 10000 miles ago. Now it is starting to misbehave again.

 

That is great advice. These switches do not typically fail outright. They become flaky and unreliable. Giving them a gentle reminder of who the boss is (gently tapping the brake pedal several times to activate/deactivate the switches) is a good way to bring a bit of life back into them (if you pay attention, you can hear a faint click as you begin to push on the pedal). So does a blast of air conditioning, believe it or not.

 

We have had to replace the brake pedal switch in my wife's 2006 XK8 twice - once in September 2012 and again in November 2016. The first time, I ordered a new one online and stored the original one on my garage shelf. The second time, I had an EE friend re-solder all connections on both of these switch assemblies, installed the first repaired one back into the vehicle, and kept the second repaired one as a spare. Unfortunately they are rather flimsy and cheaply made, but I hope my EE friend's expert repair work will hold up significantly longer than the original switches typically do. Time will tell....

 

Thank you everyone! This is why I love this forum and fellow Jaguar owners. Much appreciated.

I leave for Florida at the end of the week, if the switch doesn't come back on in the next couple of days, I will hazard the journey without replacing it first, and handle it down there. (I have so many other things to handle before the trip).

I just hope she behaves on the 18 hour journey. I will try to keep it mostly daylight driving as a result.

Unless, that is, anyone thinks that this switch failing could lead to further issues on a long journey.

Thanks again, so much, for the time and detail of your responses. They are appreciated!

 

will not using the cruise control prevent the problem during your trip? I have that message so I don't use cruise and it's not an issue.

 

That is what I am hoping myself, John. Drove her an hour during the day today with no cruise and didn't have an issue. I have the 18 hour trip from NY to FL coming up, and using cruise control would be nice, but I will just not use it to avoid that issue. I already have the replacement lined up when I get to FL. I will update this post if I learn anything interesting along the way.

 

It is irrelevant whether you use the cruise or not. The issue that triggers the amber light, warnings and cruise failure is the brake switch, so I suppose... you could try just not using the brake.

 

+1. Since the cruise control and brake lights are two separate micro switches there will be no advantage in not using cruise. I wouldn't consider driving for hours without cruise, but I'm old and my legs get very stiff if I can't move them around.

 

Good to know. Thank you. It's my first time with this issue and I am not a Jaguar mechanic. So it's not an obvious jump of logic, before reading all the forum posts, to assume that when your cruise control goes out, that it's not related (Jim).

So as long as the brake switch failing doesn't affect the mechanical brakes, I will go ahead and make the trip and fix it upon arrival.

So far it only went out for that 15 minutes and has not reoccurred. But, oh, I know it will...

 

I recall reading that at least one member sprayed contact cleaner on the switch and the problem did not recur.

 

I will give that a try, thank you, RJ237! Do you think they accessed it from the engine bay or floor to get a good spray in? (I haven't opened anything up yet to see the orientation of the switch yet.)

 

Just to set your mind at rest...

• The microswitch that is malfunctioning simply communicates to the ECU that the brake pedal is not in the full out position. This tells the ECU to disengage the cruise control. If it stays on longer than ??? seconds, the ECU turns on the amber warning light and displays "FAILSAFE ENGINE MODE" (sounds more ominous than it is.) It may also display "CHECK REAR LIGHTS."
• In all likelihood, all your rear lights including brake lights will be functioning completely normally. (Have someone check when the "rear lights" message is up if you feel uneasy on this point.)
• This issue has ABSOLUTELY NO CONNECTION to the function of your brakes themselves. There is no safety issue.

 

Roger, Thank you!

Thank you to everyone who responded.

I hope this thread will help others on their first encounter with this issue in the future. Lots of great info.

 

FYI on brake switch

Link JagRepair.com - Jaguar Repair Information Resource