OK so I have a snow storm coming went out to clean off the 03 Jag XType and the battery went dead, I jump started it and it started but it doesnt seem to go into AWD its sliding all over and it was never like that, what did I do to shut it off??? I thought it was always on????

 

03Jaguar, like you said, it is always on. For the AWD system to not "function", you would have to have a major failure of the transfer case. To get to a single wheel pulling position, you would have to have a complete failure of the viscous coupling, leaving you with essentially a FWD car. I think you may want to first check the fluid level in the transfer case. Odds are, you are going to find no fluid in the case, which could be affecting the viscous coupling. There are numerous posts on how to get the fluid back into the case and how much/type.

The only other way that I can see you having a problem is if you recently had your transfer case replaced and someone put in a redesigned transfer case in place of your 03 transfer case. This could also cause what you are seeing as the redesigned transfer case was an open differential design and this would allow for 1 wheel to take all the power and feel like you are driving a FWD car.

As for what your problem is, I think more investigation is needed to narrow things down. I think the first step to do is to drive the car between 2 people/cameras and gun the car to make the wheels spin. The trick will be whether you have a single wheel that spins, a front and a rear wheel that spins, or if you have 3/4 wheels that all spin. If your transfer case is working properly, you should have atleast 2 wheels (1 front, 1 rear) spin. If you have both fronts spin, problem with the transfer case. Both back wheels spin, most likely a problem with the transfer case, but possibly the transmission. I would think that if you had a break in anything with the rear driveline, you would be hearing lots of noise that would be making you want to stop driving the car.

Lets see what you have after this test so we can start narrowing things down.

 

The way the power is split, there is a 60/40 RWD bias. If the surface is slippery, it is possible to have the rear end step out with aggressive throttle, like a RWD car. Can be kind of fun going down the road at a 45 degree angle and opposite lock steering if you intend to do it. Not so fun if you didn't, but it takes a lot of throttle to do that.

However, to answer your basic question, the AWD is always engaged, there is no way to turn it on or off. If you're sliding, what are the tires like? Do you have winter tires, as opposed to all seasons?