My car goes into failsafe mode whenever i drive it. I called the jaguar mechanic in minneapolis and he said it could be the transmission or a hundred different things. He said the car isnt safe to drive? any ideas on what could be causing this light to come on? the check engine light isnt on and the car does not throw any codes. thanks, Jake

 

failsafe mode is a pain, and he is right, it could be a lot of things. on my car, it ended up being a bad throttle body but from what I have seen from others is it's a good idea to clean the throttle body and various electrical connectors on the MAF and whatnot. search the XJ8/R forum for "failsafe mode" or "limp home mode" and maybe you will be able to get it figured out.

good luck

 

Do you have or can you get a reading on the codes that are causing the Failsafe? If we have that information we can try to help. Your local AutoZone can read it for you.

 

my car doesnt throw any codes, and thats what is confusing me. Shouldnt it throw a code with that light on?

 

wayne:
although I have not experienced it myself, I understand a throttle boby failure can do the failsafe mode without an OBD code. I ASSUME there are Jaguar specific codes that might be read with AutoEnginuity or dealer software.

 

Under normal conditions a code is available; however, we have seen a few situations that a code was not present and it was related to the TB plugs. For now you can try a simple fix by cleaning your TB plugs, tighten them and reinstall the plug and see what takes place. This might help http://www.gusglikas.com/AutoRepTB.htm Let us know how that works.

 

okay i am going to replace the brake switch, do the TB connection work, and anything else i should consider?

 

i live a long, long, long way from a jaguar dealer, so i have no way of getting a jaguar mechanic to look at it, and it is really frustrating for me, so anything you guys can think it could be, i would appreciate some tips

 

Just cured mine with the brakelight switch

 

I had the same problem with my 2004 VDP. First step was to clean the Throttle Body and and recalibrate the sensor. This worked for 3 months and then had the same problem again- driving along and car goes into limp mode when removing your foot from the accelerator. Jaguar dealer scanned and determined that the Throttle position sensor on the side of the Throttle Body was bad. They also said that this was a common problem, but not enough for a recall of course. The TPS can be replaced except for the fact that it can not be purchased seperatly. It comes attached to the TB and you have to purchase the whole thing. To the tune of $1260 U.S. installed.

Having reseached and spoken to other Jaguar drivers, this price actually was not as bad as I had heard and seen. Some where $3000.

car is working fine now and enjoying the car again. ...the price you pay to have such a fine vehicle.

 

Had the same issue on my 99VDP....
After searching and reading all the posts, I decided to start with replacing the brake switch. $70 later the warning light is gone and I can use my cruise control again...
When I pulled the old brake switch out, I tested it with multimeter, and found that even in "closed" postion, the micro switch had a resistance of about 30ohm, as opposed to ~0... That was enough to trip the computer into thinking that brake is being applied. If I had more time, I could have soldered on a new swith myself for less than $1....

 

If you end up with wanting to replace the throttlebody, there is a place in Tenn, which will check your throttle body and rebuild it for $299. They rebuild CPU/ECu's, ABS sensors and throttlebodies. There are a few of us who have had our brains rebuilt with great success. Check Jamesjag thread for the info. At this price, itz cheaper than having the dealer just look at it. They list rebuilding on ebay. Their user name is ate1234. I can send you a link or phone number if you want it.

 

After consulting with the experts here, I was told the following:
Take the Jag to the dealer, and tell the the service manager to tell the mechanic to set a OBDII code to identify the problem. Get a print out of the results. That way you are not getting charged for something that is not wrong with the car.

My problem was the cruise control module.

Good luck and I hope it's not a major item.

 

Keep in mind that the vacuum system does not start and end in the engine compartment. Kudos to you for finding the problem. On the road again!

 

just cured my other xjr with a brakelight switch

 

I had the same issue....in my case i had to have the throttle body cleaned and that solved the problem for about 6 months. Then it started again. Drive along at 70 mph and when you would let off the accellerator it would go into limp mode. Pull over, turn off car, restart and it would run fine til I let off the accelerator again.

Finally had to have the sensor on the throttle body replaced...only problem is- Jaguar does not sell just that sensor...it comes on the throttle body so you have to buy the whole thing. I saw some quotes as high as $3000 for this at Jag dealers and non Jag repair shops. Nalley Jaguar in Roswell, GA did it for me and was very fair with price and did a great job. Very good staff and techs. It cost me about $1300. I have not had a problem since and it runs great.

2004 VDP.

Steve

 

Good to see your ride runs well and thanks for your feedback as well

 

Is replacing the TB unit a DIY job, or are there special tools to R & R this item?

thx

 

I would do a TB myself, as I had to remove it to get the supercharger out.

I am reposting here again, because the first car I fixed earlier in this post has the problem again, but it presents differently. Before, when I applied the brakes and the car was in cruise control mode, it went into failsafe. I replaced the brakelight switch and the problem was solved. This worked for my other xjr as well. Several monts later, the first car I fixed goes into failsafe as soon as I push the button to enable the cruise control. I would be interested in knowing both the location of the cruise control module and its part number.