Fail safe mode help

(sawyer10702) #1

Hello my first time posting on our 2002 xk8. Recently it went into fail safe mode but only when my wife drives it. After turning it off for half hour it’s fine. Then some times it will do it twice in one day. It’s on short distance stop and go to places. And then it won’t do it for a while. Now I did have problem with abs traction control light appeared so I changed the two front wheel sensors and that is ok for now. I have no codes with scan tool. Any help in the general direction would be appreciated.

(bdragon) #2

This is fairly well known unfortunately to owners of AJ-V8 powered Jaguars.

  1. does this occur only when the cruise control is engaged? If so, then the fix could be relatively cheap (brake sensor switch.)

  2. if not related to the cruise control (happens when it’s off) then it mostly likely is a more complicated and expensive problem (the throttle position sensor on the throttle body.) As of a couple years ago, this part was not available separately and required purchase of a new replacement unit ($$$$.) Some people have picked up used ones with success. When I experienced the problem, I sent mine off to a repair place that got it back in action for a fraction of the price of a new one.

If you think it may be the 2nd expensive case, search the archives using the keywords “throttle position sensor” and you should be able to find more on this topic discussed in depth.


(Bob Allen) #3

We have the same problem, it happens periodically. According to others and my own experience,

A very sharp brake action to stop at slower medium speeds can temporarily cure the problem. the bad
part is that you risk putting a flat spot on your tires. Better is to air hose (yourself or your shop) the entire

brake/tire systems and finally the replacement. Best and least expensive way is number two. I’ve done all

three and my preference is air blow. For cost and duration of repair, I’m sticking with that. Including by the

end of this month. Best, Bob

Bob Allen

(sawyer10702) #4

Dave no difference with cruise on or off! The only difference this time the check engine light has come on now will check codes this weekend and post them. Think I will try cleaning throttle body. I have all extra sensors i can change one at a time to pin point.
Cheers mate

(sawyer10702) #5

Bob thanks but I’m not understand message. You mean air blowing.the brake system has in blow dust out of sensors. The issue now stands the check engine light is now on. I will check codes.And post there has to be a reason why this is happening. Maybe a computer ground?

(Bob Allen) #6

I had been told to blow compressed air in around the sensors. Found that it did not always work.
A fellow member of JCNA suggested blowing all of the brake area, it worked.

Bob Allen

(sawyer10702) #7

So I put on scan tool and one code was found p0121 throttle position sensor. I removed plug from tps and cleaned connections. I took the xk8 50 Mike trip no issues so far. Maybe moving the harness has made a.better connection my wife is taking it to San Louis Obispo tomorrow so quiet a trip i will post the outcome tommorow. Thanks for everyone’s help so far. Another note why is my airbag light on my car is LHD it’s on right on wood near top globe box?

(Bob Allen) #8

Wonder if that’s the heads up for the passenger side airbag? My xk8 has one and my

Range Rover Sport allows me to turn it off & on. Guess I’ll pay more attention this weekend.


Bob Allen

(Grahame Loader) #9

Do you have anything sitting on the passenger seat?

(sawyer10702) #10

Bob i figured the air bag light it comes on only when there is no pasenger😁

(sawyer10702) #11

Grahame yes no passenger light comes on cheers mate.

(sawyer10702) #12

So my wife went on her 400 plus.miles round trip no problems! So was tps harness needed some movement. Now I need to fix my hvac codes 23 refrigerant pressure switch! Just be near compressor. And 33 cool air bypass potentiometer harness. The heater does not get very hot? Any he!p. I heard you can jump 2 pins to get.compressor to kick in maybe at the relay. The code 33 where is that located? Thanks.for the help