Jaguar x type 2002 heater blower starts going on max even if car is switched off and locked. flattens battery overnight.

Looks like you have two questions in one:
YES - the 2002 S-Type does have an onboard computer system however it is extremely hard to avvess on your own. Most any Jaguar service center can probe the system to find where your power drain is but it is usually quite expensive to have it done - on average between $150 & $200. H8wever, it will give you a complete breakdown of everything that is wrong.

second
Yes - if you lock your doors on the 2002 the passive security system engages no matter how you lock them. The system can be defeated or disconnected by a service center or dealer but it is such a low power drain that it shouldn't have enough of a drain to affect the total power of the battery over a month long time much less overnight. Most likely th drain is from another source.

Sorry for the bad news but that's all I have without knowing your individual car better. All the 02-03 S-Types have frequent electrical problems - it's their chron

It is likely the fuel pump safety switch, search for a solution online but, some0most cars this happens to after an accedent for obvious reasons. Probably not a big deal, the dealer of a shop may even be able to help over the phone or even maybe just disconnect the neg. battery terminal and this may reset it. Good Luck

details of the cut off swich can be found here :-
http://www.rover-400-series.co.uk/cutoff.php

Check the little pump below the brake booster for running and the coolant valve for movement.

Both hoses to fire wall should be hot.

Check for air lock in system.

Blend doors on this vehicle stop working....common complaint.

To verify Blend door movement, turn on ignition with engine off.

Run temp to max and the min..... listen under glove box for ( sliding ) motor noise as door swings from hot to cold.

This is a digital system needing a Jaguar scanner for diagnosis.

Make sure your cooling fan isnt coming on after the car has been parked up for a few hours, this will flatten your battery. Yeh.

try this,with the key,unlock/hold key over for 30 secs (windows will go down) .then lock/hold key over for 30 secs.(windows will go up,then lock the car with the remote,you have just reset the autoclose facility inside the computer.may help!!

Hi. This will be the result of a failed resistor switch. the switch controls the current level sent to the blower motor. Once replaced, the motor will operate at your desired rate. This switch is an integrated part of the AC/Heater control cluster, that is mounted in your dash. You will need to remove the trim, and cluster assembly to expose the damaged switch.

Had the same problem, it turned out to be the sensor switch on the transmission. I was also told to disconnect the battery overnight so all can reset but that did not help in my case.

TRY STARTING THE CAR IN NEUTRAL.

If your battery is older, it may be leaking acid... which goes right down to the negative connection wire.... if that eats throught then you have no circuit.... happened to my car. Go take a look at your battery cables.... also, check the battery fluid levels... even though you hear it is a maint. free battery - sometimes you still have to add water now and then!