Hello all...

I have written in the past about how my amber failsafe engine mode was really starting to upset me because everytime I hooked up a computer to read codes... it came back with NOTHING!

Left twisting in the wind with nothing to do but try to run thru different past articles and random troubleshooting I was finally able to deduce that it only comes on when my cruise control master control button below the "J" gate was in the on position.
I do not have to set or activate the cruise at all, but I finally noticed that it will not go into failsafe until I activate the master CC button.

Turning the botton off will allow the failsafe warning to go away, although I haven't seen it turn off itself. the warning message will be gone whenever I restart the engine.

Any thoughts?

 

It is not uncommon to get the FailSafe mode on an XK8/R with the cruise control on. The fix has been a brake switch. I am not sure your XJ falls into that same scenario but it is worth looking into.

 

Great observation Watson (joking), I've the same exact symptoms, when cruise control is on I get the failsafe message as well. When it first happened I got the code reader out and got the code P0456, which is a small emissions leak and thought the two where the same issue. I did the most effective thing for an emissions leak and bought a new gas cap for $23 from the dealer. I cleared the codes but the failsafe message would not go away. after reading your observations yesterday I turned my cruise button off and the failsafe message has gone away. I checked the codes again yesterday and the only code I get is P1111 which essentially means I have no codes. I feel better now that buying the gas cap did actually take care of the P0456 code. I think from reading everything here and other sources on the internet that Gus has hit the most likely cause on the head.I believe the part number for the brake light switch with cruise is LNB6420BB and can be purchased from the dealer for $77, can't find it anywhere else cheaper. This is supposedly a 5 minuet swap that will probably take me an hour. Here is another link from this site that will help with the install and other discussions "https://www.jaguarforums.com/forum/xj-x308-xj8-xjr-27/yet-another-failsafe-engine-victim-38998/"

 

I have also been wondering about the cruse control system and fail safe/ restricted mode. I wonder how much of the cruse control system is operating when the button is "on".

I have never experienced a RP event while the cruse control was in operation or when I hit the brakes. I only get mine when I am on the throttle -- and I used to keep my CC button "on" - now I have it "off"

I am beginning to believe that my problem is a TPS -- and if most of the cruse control monitoring system is working when the button is "on" it would stand to reason you would be more at to have an error detected.

 

Update - I replaced the Brake Switch, part number LNB6420BB and no more failsafe mode. The part cost $72.25 at the Jag dealer, cheapest I could find. DJsomebody did you ever fix yours? Today all warnings and codes are updated, tomorrow is another day.

 

Kudos to you! Good to know the suggestion helped.

 

Good day
i am the proud owner of a Jaguar XJ8 with a problem.
sometimes when i put my car in either reverse or drive, engine fail safe mode kicks in with the restricted performance and strange humming. Scares the heck out of me. This difficulty leads me to believe it is a problem with the transmission although i am mechanicaly challenged.
Any thoughts on the problem or how much it would cost to repair it would be greatly appreciated.
(Sorry i sent this as a reply, I am new and dont yet know how to post as a thread question and you seem very attuned to jag issues.

 

I'm getting the failsafe engine with an amber light and I loose the cruise. I will be trying the above fixes ASAP. thanks brothers.

 

So I have two xjrs and have had this issue a few times in the past. The brake switch has always worked. My luck has run out in that it did not work this time. The failsafe happens when the speed drops below the set point for the cruise control. And ideas? Is there an actuator somewhere?

 

I started getting the problem yesterday and immediately thought 'this is going to cost me"!
I noticed that the cruise control wasn't working so I will change the Brake switch.
THANK GOD FOR THE FORUM.
Keep happy
Jim

 

Replaceing the brake light switch fixed my 2000 xjr when that happened to me.

 

Yup, same here! Thank god for this forum is RIGHT!!!! One little switch, a bit of bonding with my car, and it's fixed!

 

It was indeed the brake switch for me. Changed it and it did the job. Thanks a million for the suggestion Gus.
Funny story, and a testament to how much I love my XJR. I did the brake switch replacement after I blew my head gasket and wound up having the entire top end of the motor rebuilt. I had a slow water leak and one night it caught up with me and I overheated. I tried to do what I could along the way but never did what I needed to repair the leak.
After a compression test, my tech concluded that my gasket is blown.
What the hell do I do now...
The only thing a true Jag lover to the end would do. A total breakdown and replacement of the gasket, a total valve and lifter rebuild. Timing chain/ belt, new pulleys. A total package from the Mina Gallery with the SS cat back Borla exhaust. The cold air intake, and the supercharger pulley upgrade.
If that wasn't enough, I went on a crazy hunt to find racing cat/ downpipes so that the exhaust is done. I found a company called Nameless performance out of California, and they built them for me to order.

What a car.

Passes NJ state inspection for emissions and I'm all set.

Now as long as my wife doesn't find the receipts, ill keep my marriage.

Brian

 

it was the brake switch in my case

 

Gus, thank you for the reminder! I'm experiencing the same issue for the second time in 5 years. I had forgotten what I did to fix it the last time. You'll need an old towel and a can of WD40. The brake switch is up underneath the brake pedal... Set your towel on the floor to catch all the excess spray, and spray up behind the brake pedal. Use a lot! Worked the last time for me, and I'm going to try it again after work tonight.

 

I did the WD40 fix 2 nights ago. The failsafe light did not appear for 2 days and the cruise control worked faultlessly. Great diagnostic aid to confirm I need a switch. Where can I get a video of the replacement? Only ones I find are for XK8's.

 

If the brake Switch fails it should give a code, at least it did on mine at the time. The other thing is, what code reader are you using. In my experience the Jaguars are finicky at best to show codes on generic readers / OBD analysers. So I have two readers that also show Jaguar Specific codes.

Unfortunately, absence of codes doesn’t always mean all is well.

Good to hear the problems appears to fixed!

Jeroen

 

The fix for the Brake light / Cruise Switch is to remove the switch, take a small drill bit about 1/8". Be real careful and drill a hole in the side of each switch. Use a toothpick and dip it into a small amount of WD40 . Allow it to drip into each side of each switch.Shake it to allow the insides to get wet.Let as much as you can to let it drip out.I have had to buy a new one with the first Jag I had but not anymore.

 

What code came up on your scanner for Brake Switch failure? I think I'm having the same issue. A P1111 and P1121 came up on my scanner.

 

You can (and should) look up codes in the free downloads on here and JagRepair.com - Jaguar Repair Information Resource

All P1xxx codes are make/model-specific so do not use random meanings off the net!