I remove the positive cable to reset my system. In the morning I try to open the trunk and the key won't turn! It's like it's the wrong key. But it's worked fine before.
What do I do? The positive is not connected and the key won't work.

 

Minister, commit thyself to the search function!
You will find +Batt and ground terminals under the bonnet, suitable for attaching a booster battery to for the purposes of opening the boot, but insufficient for jump-starting the car. (please accept the statement as good advice, not as a challenge to try it....you may fire it up....but woe is the genie you unleash on the unsuspecting electronic modules throughout your car)
Meanwhile, get some graphite and or penetrating lubricant and work that key in and out of the boot orifice until you can successfully actuate the latch with it! Now go 'round to the driver's door and do likewise! Rinse and repeat at least monthly if not weekly!

 

This should be of some help:

https://www.jaguarforums.com/forum/s...ng-port-87362/

 

I need to know exactly where to find it. You want me to blow out my car?

 

Please re-read the thread linked above. If you can't access the terminal just aft of the right front tire, it's no big deal. The same thread also describes how to supply power via the fuse box under the hood.

If you have a spare battery, that would be the preferred way to supply power. It will put out a nice 12ish volts DC. A battery charger might work, but some put out 15ish volts, and some use some fancy AC waves as part of the process. All bets are off if no battery is connected, as there may be some big voltage spikes. A nice smooth DC supply from another car battery is much better.

 

I can get the 12 volts from my other car. I read that thread but they were using a trickle charger. I was worried a car battery might have too many amps. It made no sense as to why they wouldn't just use another car. Not to mention, the dealership tried to scare me saying I could blow out the whole system.

 

you cant hurt it if you get the polarity and voltage correct , e.g + to + and - to - 12v .
positive goes to the power jump point behind the under guard .
negative can go to any bare steel part of the car , eg wheel stud engine casting ect.
you can use a jump pack , jump leads .

or you can if you have a 16a 12v battery charger use that , it will be sufficient to just pop the boot/trunk .
also you can on some speck s types , fold down the center rear arm rest , then reach through ad pull the rear seat poppers .
fold down the seats then refit the bat terminal with this access .

 

You're in a unique situation because your battery is disconnected. That thread was written for a battery that is connected as normal, but has gone dead. The charger connection under the hood was a lifesaver when the battery has gone dead and then you discover the key doesn't work on the trunk.

It was a two-part story because it also covered a convenient way to hook up a trickle charger to keep the battery topped up on cars that are not driven frequently.

For your situation, you would have to extrapolate a little. You can still get under the hood, so that is your best/only access to the electrical system. You only need to momentarily energize the electrical system so the key fob can unlock the trunk. I suggested not using a charger simply because it might put out a funky voltage pattern without a battery. So for your situation with no battery, clean DC from another battery is your safest bet.

For the other situation with the battery connected but dead, the use of a charger is way easier than lugging around another battery. And for keeping the battery topped off, that's a job for a charger.

Concerned about too much amperage rushing in from the battery you will be using? Just rig up a fused test lead to connect the battery. A 10 amp fuse would probably be plenty.

Be aware the alarm may sound when you apply power. Don't let that startle you.

Just curious, what did the dealer suggest?

 

I suppose you could get one of those little "keep alive" adapters that plugs into your cigar lighter and attaches a 9V battery, like many smoke detectors use. Plug that in, turn your key to position II in the ignition, and pop the bootlid from the instrument panel switch.

 

Probably worth checking the disconnected positive cable isn't shorted out to ground before powering it up.

 

Just let us deal with the scary problem and don't forget your cheque book.

 

Once you get past the current problem... next time disconnect the negative as the workshop manual etc say - it's safer (think about it or ask and I'll explain) as you do it and also it can't result in the positive one perhaps lying on a body metal part (see Norri's post).

 

A Clavenesque tangent:

Year ago, I was taught the same basic thing, but with one important difference. Always disconnect the ground cable. Not much of an issue these days, but on the rare chance you're working on a car with positive ground (older English cars and older Fords), the ground cable is always the safe one to disconnect, not always the negative cable.

 

The dealer suggested bringing it in of course

 

Do you mean an ECM Memory Saver?

 

Yes, definitely the ground one. (Being in this forum, it's the same as the negative, but as you say on some older cars it isn't.)

 

I don't think a 9V battery will supply enough current. When you turn the key to run or acc (so the lighter outlet is connected), enough other stuff may also power up and exceed what a 9V battery can supply. It won't hurt anything to try, but don't hold your breath.

 

Could be.....you could always pull fuses from all the equipment and modules you don't want/need to power before turning the key on. OR...just get a cigar lighter power adapter with a couple leads on it (don't most people have these laying around from long-dead heated coffee cups or similar electronic equipment?) and attach the leads to a 12V car battery.

I've got one of those on a pegboard somewhere...tried to use it once to keep module settings alive whilst pulling the battery....forget which car....but the 9V got awfully hot in 5-10 min. It is better with the Fords, at least the older ones, which have hot-all-times power points and thus no need to turn the key on.

 

I tried the keep alive cigarette lighter module. Didn't work. I tried this Wagan EL9796 Easy Quick Jumper In-Car Jumpstarter

Still no luck. I'm trying the fuse box next I guess. I'm trying to go from the least dangerous first. Or maybe the post under the wheel well. But I wonder if the positive cable being disconnected from the battery is going to affect that fix. Won't the circuit still be open?

 

I should think the only way that would cause a problem is if it is in electrical contact with ground.