Hello everyone

I was driving around and everything is going fine and running smooth. I rolled up my windows and went in a place to get some food and when i came out and tried to roll down the window it does not move. there is a click noise so i know it has power and the moon roof closes on it's own after ten secs. i read on another post that i should disconnect the battery wires and touch them together to restart the computer. Here is my problem which battery do i do this to there are two batteries in the truck on double and a single?

 

Thanks to the fellow members of jaguar i found another person with same problem and i gave them thanks on there thread and now everything is running fine i disconnected the negative cable from battery and touch the positive for about ten seconds. problem cleared and radio works fine,

Thanks again everybody

 

glad to hear you were able to find a fix - I changed the title showing resolved status

 

I'd like someone to clarify the instructions given, and what they are supposed to do.

I have performed a "hard reset" on the ECUs in my car by disconnecting the ground/earth line between the battery and the chassis and keeping it disconnected for a couple of hours. The "couple of hours" is probably too long, but since I wasn't going anywhere it just stayed disconnected until I had the next trip to make.

When I see/hear, "disconnected the negative cable from battery and touch the positive for about ten seconds," it creates the image in my mind of someone shorting the battery, which would be insane (and dangerous, too). You're certainly not touching the positive terminal with the negative cable, so what is meant by "touch the positive for about 10 seconds?"

 

Yes, you do touch the negative cable to the positive battery cable and post. It sounds dangerous, but, the negative side of the battery is disconnected, so there is no short. This discharges all the capacitors and resets the system. At least this is what I have heard. Anybody jump in and correct me if I'm wrong. I've done it a few times. I can tell the computer has been reset by the idle sort of "hunting" for the right spot after I start the car, and the long term fuel trims go to zero.

 

So, let me get this straight:

1. The negative cable is disconnected from the battery terminal itself, but not from the chassis.

2. One touches that cable, disconnected as noted above, to the positive terminal of the battery?

If this is the case I fail to see that it would have any effect at all, since the positive terminal is already connected in such a way as to be in contact with the chassis of the car. Making it "more in contact" with the chassis amounts to "much of a muchness" that should have no effect.

I will be genuinely happy if someone can explain why the suggested fix should have any effect.

 

No, it is not ... at least on a vehicle with a negative ground system such as all recent Jaguars.

 

You are absolutely correct. If it were then you'd have an instant short circuit.

I don't know what I was thinking or trying to say when I typed that. I'd still like to know what the definitive underlying explanation is for the technique originally offered.

 

The effect of shorting the negative cable to the positive cable, after disconnecting it from the negative battery post is to drain the residual current from the keep alive memory and supporting capacitors. Just like a reset on other electronic devices.

 

I understand how everyone feels about the negative touching the positive. I was very nervous about actually doing this procedure but I ran out of any other options without spending money. After I talked to a couple mechanics they told me it was fine. What you have to watch out for is if the positive touches negative not the other way around. The positive wire acts like a road leading in one direction it pulls power from battery creating a charge so when you touch the negative that's how you get a spark. when doing it the other way the ground wire is just pushes the remaining power back into the battery. without frying anything. I know this is not a smart sounding answer. So if any others can make it sound more understandable please feel free to help.

 

There is no effective difference between removing the positve battery lead from the battery and touching it to the negative lead or removing the negative lead and touching it to the positive EXCEPT, it is safer to remove the negative lead because if you let the wrench touch the chassis while loosening, it does not cause a short!

When either lead is removed from the battery, the load (the car) is disconnected from the source(the battery). If you waited 30 seconds, all voltage in the load will dissipate without any touching (I have measured this), but until then, about 750 millivolts shows on the load side, and some believe that voltage can keep up some memory. (I doubt that!)

Suit yourself. Either disconnect, wait 30 seconds and reconnect, or disconnect, short the load side and reconnect immediately.

 

glad to hear you resolved this...as i had the same problem this summer....perhaps you saw my post....the thing is however....what you need to know....by resetting without using a connection/saver.....you will wind up re-setting the computer.....no biggy ordinarily...unless you need to go to inspection as i had to.....to only find out...my emission control settings were re-set to zero.....and the inspectors could not do any emissions testing so they failed me....i am currently driving the car all over the place to get these readiness codes released for inspection....

 

I could not get the driver door window to operate and the sunroof would close itself after about 10 seconds.

I was skeptical, but I did the "hard Reset" and was amazed that it solved both the window problem and the sunroof problem.

Thanks for this information. It was worth it's weight in gold!

 

You will need a drivers door latch.
next time it happens, do the hard re set but do not use central lockinf transmitter to lock un lock the car, use the key in the door tumbler