I'm Wolfgang from Augsburg in southern Germany and have been the proud owner of a 2004 XK8 Convertible 4.2 for about a month. The car had been standing for several months before I bought it and had a deeply discharged battery, which I replaced with a new 95Ah battery. I have also measured the quiescent current consumption, which at around 210mA is clearly too high. The car has a premium sound system with CD changer, a Jaguar built-in phone, and a navigation system. There are no other extras or aftermarket accessories. I checked all fuses for voltage drop and measured a voltage drop of approx. 0.8-0.9mV in the fusebox on the left side of the dashboard at fuse 5 (lamp supply 2, body processor module, 15A). According to my table, this corresponds to just under 200mA and thus to the majority of what I measured in terms of quiescent current consumption.

Then a fellow enthusiast made the incredibly kind offer to read out the car's errors. After the readout session with WDS/SDD, I am now a little further along. We deleted the historical error codes, took a test drive, and then did a new error check.

The following error messages appeared:

1. Body processor module U1041 (travel speed not received)

2. Lock control unit U1041 (travel speed not received)

3. Drivers door control module B1236 (window feedback signal, pulse loss between distance end points)

4. Passengers door control module B1236 (window feedback signal, pulse loss between distance end points)

5. Lock control unit B24BD (DTC invalid)

6. Vehicle protection and lock control unit P0110 (no information available)

7. Engine control module P1582 (crash recording data available, freeze frame data...)

Of course, I would be very interested to know whether one of these faults could be responsible for the increased quiescent current consumption in my car, which, according to the voltage drop measurement, can be traced back to fuse 5 (lamp supply 2, body processor module, 15A) in the left fuse box on the dashboard, and how I could solve the existing problems.

Many thanks for your recommendations!!!

All the best, Wolfgang

 

How are you measuring the voltage drop on that fuse? The doors need to be closed and the car locked and left long enough to go to sleep to get the lowest current consumption.

Also the voltage drop is really just a guide to the current consumption - you need to pull the fuse and measure the actual current with your multimeter on amps to get an accurate value.

 

Are you following the correct procedure for testing ? Are you allowing time for the systems to shut down ?
It will take about 60 minutes for the electronics to completely shut down to lowest current after closing/locking.
I made a graph from my 4.2 XKR showing shut down currents measured over a 120 minute time (see below). A current of about 200mA, or higher, is normal for about the first 50 minutes.

 

Hi Dibbit,
thank you for your answer. I have left the car sitting with the drivers door open for more than 60 minutes and then measured the voltage drop on the fuses without pulling them just to have an idea on which fuses I have a voltage drop in general. After that I have pulled fuse 5, closed the door, locked the car and waited for one hour again. After that I have noticed that the quiescent current consumption went down from about 210mA to under 50mA. Based on that I think that I could indentify fuse 5 as my problem area.....

 

Hi Derek,
I have waited for 60 minutes or a bit more before my checks. Then I left the meter attached to the car for one night and still had the 210mA in the morning. But I will recheck that based on your recommendation to be absolutely sure. Thank you!!

 

Hi Wolfgang
For my graph (post #3 above) I used a multimeter with built in datalogging and connected in series with the battery ground -ve connection, with the car fully locked and alarm set using the key FOB
The power amplifier in the boot of cars fitted with the premium audio system has been known to cause discharge problems, supplied by fuse #18 30A in the fuse box in the luggage compartment/boot.

 

Hi Derek,
thank you for your helpful advice. Although not being part of the error codes received this could also be a source of my problems. I will check that out today.
Wolfgang

 

I wouldn't worry about your error codes - just look into where your current drain is coming from (if indeed it is excessive). Do you have anything not working on the car, or is it just the battery drain that you are concerned about? You probably just need to make sure your battery is fully charged and drive the car.

 

Hi Derek, I have pulled the 30A fuse Number 18 in the boot (power amplifier). Unfortunately no change. The quiescent consumption remained at about 220mA. Car has been sitting locked in the garage overnight before measuring. But thank you again; it could have been a solution....
Wolfgang

 

Hi Dibbit,
thank you for your comments. You are surely right, I should not worry too much! But on the other hand the quiescent consumption is about 210/220mA and should be 30mA, so I would like to explore the reason somehow....
Thks again, Wolfgang

 

First thing to do is get the electrical guide for your car and list out everything that is supplied by that fuse. You can then go through each item unplugging it to see if the drain goes away. Or remove the fuse and see what no longer works.

 

Hi Dibbit,
thks!! It´s fuse 5 on the left side of the dashboard, which supplies "lamp supply 2 and body processor module". If I pull it, the consumption goes back to the recommended value. Based on my limited electrical knowledge I could not find in the electrical manual which other fuses I should pull next in order to learn more. But I will try my best to check....
Wolfgang

 

That does unfortunately look like it's a permanent supply for the BPM (assuming your car is LHD and the fuse box is on the driver's side).

You could try pulling relays out one by one, just in case one of them is stuck in the on position.

You should also go through every switch in the car and make sure literally everything works as it should - maybe you'll find something that is not doing what it is supposed to.

Edited to add - if you still have access to the WDS/SDD you could have a look at all the live data for every input/output and see if everything makes sense/nothing is stuck on.

Another thing to check is the flap in the ignition switch barrel - this should close when you pull the key out. Make sure this is opening and closing ok.

 

Thks a lot!
I have pulled all relays one by one. No changes here.
Have tried the function of every single switch. Everything works properly with the exception of the electric seats. Here some switches seem to work sometimes and sometimes not.... Moreover that my car still has the problem with the too long outer cables of the electric headrests. So the electric headrest motors start to work when putting the seat backs forward and then back to driving position.
Unfortunately I do not have access to the WDS in the moment.
The flap of my ignition switch barrel opens and closes properly (only a very tiny slot remains open, when pulling out the key).
All the best, Wolfgang

 

I think the flap is closing far enough, but you might want to lubricate it all the same. For the seat switches they are probably just dirty - with the ignition off try rocking the switches back and for multiple times to try and clean them up.

I'm not really convinced its worth doing too much more investigating on your current drain if the car is all working otherwise. The BPM module is behind the glove box in not the easiest location to get to. You could try unplugging the harness at the BPM itself to confirm the current drain goes away, before cleaning the connector with contact cleaner and reconnecting it.

It seems likely that either something else is keeping the BPM awake, or there is a fault on the BPM itself. I believe that as your car is a 4.2 a replacement BPM needs the VID block programmed (someone else could confirm this) so swapping modules isn't that straightforward either.

Unless this current drain is causing you a real issue, I would be very tempted to ignore it - if your car works, don't break it.

See if anyone else has any ideas not already covered.

 

Thks a lot for our comments!!!
I have lubricated the lock yesterday when checking the flap position. So I can tick this box!
I have to check on the seat switches. Have to deal with shortening the outer cable of the headrest adjustment, too, so there is a little bit work on the seats anyway. But that´s fun!!
After learning a lot from forum threads I would have the same idea concerning the BPM. My car is a 4,2; I also read elsewhere that just replacing the BPM is not enough....
I will concentrate on the following errors:
1. Body processor module U1041 (travel speed not received)
2. Lock control unit U1041 (travel speed not received)
Maybe these errors prevent the BPM from going to sleep.....
I will investigate a bit further, but your idea to just let it as it is sounds also tempting.
Thks again for your help, Wolfgang

 

You should download the wiring guide for your car from Gus's site "Jaguar XK 2003":-

JagRepair.com - Jaguar Repair Information Resource

Spend some time understanding the electrical guide as it has answers to every question you have about the wiring/connectors/test values etc.

You might also want to get a more advanced code reader such as the Foxwell scanner or if you are competent around a PC the Jaguar IDS/SDD and a Mongoose cable.

And finally, put some kilometres on the car and hope the codes go away.

 

If you switch the BCM module via the ignition then the drain will go away when the car is not in use.

 

Hello Dibbit,
thank you for the link! Is the wiring guide part of the workshop manual? I could not find a wiring guide in Gus's site "Jaguar XK 2003". Sorry, maybe I just could not find it?
My fellow enthusiast has the WDS system with Mongoose cable and I was able to detect the errors based on that. I am thinking about buying a laptop based system for me, too.
Wolfgang
,

 

Thks a lot! I am not sure whether this is a viable solution as I had to notice that e.g. the central locking does not work anymore when pulling the fuse for the BPM. Or am I wrong? I do not have a lot of experience concerning this.
All the best, Wolfgang