Hi Guys,
Been up and down with wifes 99 Jag XJ8, 85K. I figure out one problem and happy then WHAM, another then another. Finally parked it for nearly a year to save up funds to repair. All sorts of engine/emission codes so decided to start upstream at the fuses, then plugs and work back. All OK. Was going to replace MAFS, then, then knock sensor, then 02 sensors, then 02 heaters till I got it all. Already cleaned throttle valve, MAFS, and all connections I could find as well as cleaning all grounds I could find.
Major problem before was 5 of the 7 emission monitors would not reset, O-2 , knock sensor, 0-2 heater codes, etc, thus no emission sticker which meant can not register which means can not drive without risking jail. Told wife she could drive it anyway and she said "(censored)".
Now, scanner does not pick up anything at all. Completely dead! Tried scanner in another car and OK. No use in going forward if I can not tell if I am going forward without the codes, or lack of.
Any ideas, do I need new computer(and which one?) or time for the junk yard?
My wonderful Brit wife loves this car as her father and favorite uncle raced Jags as did her Grandaddy who raced pre-WWII at Brooklands.
Any ideas appreciated.

 

Could it just be that the battery is low?

 

I had run the car quite a bit to charge up and it comes in right at 12v, exact reading of our other car.
Thanks

 

something is wrong with the car but its best if you just dont give it up. It could be the computer itself. you can get them rebuilt or find a used one on sale

 

Hi, the 12v supplys to the socket for the code reader are fuse protected, check your model/year electrical drawing
Bob

 

you're a little far from me to let you come over and use my scanner, but you obviously need to find one that talks to your jaguar. It may cost you a $10 more than an online purchase, but the autoparts stores usually use the same machines to scan cars that come in that are stocked on their shelves. It could be the only way to 'test' and confirm before buying.

 

Thanks guys,
Bob, I downloaded the JTIS and I'll be darn of I can find the wiring to the socket. Will keep looking.
Matt, thanks, but this scanner worked fine on this car till I took the Jag out of storage.

 

Hey Bob,
Spent the afternoon learning how to read electrical diagrams and finally found the data connections in the CAN wiring section rather than the ECM where I thought they would be. Traced straight back to a heelboard fuse box I thought I had checked every fuse on. Guess the one fuse I missed was the one that was blown. Scanner now works fine except for the codes it is reporting(lol).
Thanks for your help and hopefully I can move forward.
I know I soon will have to start a new thread regarding emission monitors not recycling. Any thoughts from a pro like you?
My O2's before Cat are both reporting bad codes so replacing one to see if it is an upstream problem or the sensors. Right now trac/stability comes on at start-up but then goes away after long idle and restart. Thinking low battery since car has been in storage and getting a new charger(mine died) to see if that helps.
Again, Thanks so much.

 

Hi,
Glad to be of some help but I,m no "Pro".
You have a few issuses still then. Regarding trac/stability warning there is lots of information on this site regarding this problem, from my own experience its always been either poor contact on the sensor connector itself, and a squirt of electrical contact cleaner has cured it or theres been a break in the conductor in the cable to the sensor because of the flexing on the front wheels, the break is not visible a resistance test on the cable from the connector under the bonnet while someone is turning the wheel might show it up.
What codes are being reported?
What Scanner / Program are you using?