The attached write-up on Quiescent Battery Current Drain may prove of benefit to Jaguar owners. While the focus is S-Type, because that is the forum in which this issue was explored in detail, the procedures and JTIS references are applicable to a broad range of models. I was asked to bring these procedures together under the broad theme of “what is it?; why is it important; and how do we measure it”.

Owners may arrive at this issue as a result of unexplained and ongoing discharge of their vehicle's battery, despite continual re-charging. Logically, they wish to diagnose whether some on-board electrical or electronic equipment or fault is causing an unexpected current drain, despite the car being locked away for the night ... asleep.

Many thanks to all who contributed to this subject across many forum threads, and to Graham [GGG] in particular, for his patient help in preparing the PDF for you to download. Any errors that may remain are mine alone, so I encourage your feedback.

Regards,

Ken

 

Good one Ken.

Added to FAQ's under 'Miscellaneous' section.

Graham

 

Might be worth adding this (note the warning about the electronic throttle)

Also, I mention again that it can help to see what's drawing power and roughly how much by measuring Voltage (in mV) across the tiny metal conductors at the very top of each fuse (they look like little metal dots).

 

Thanks for the feedback fellas ...

[JagV8] raises, and supports with a good link to the Jaguar recommendations, some very important issues. I applaud the warning re electronic throttle may exceed multimeter rating, but again emphasize that I go further ... all power consumers off; remove key; undo battery neg cable; insert meter; lock car ... and for three good reasons ...

• whilst the "fuse pulling" I advocate may be "old" because it is too time consuming for a modern commercial workshop (I agree); time is one commodity our members can apply with no added cost;

• equally, clamp meters for accurate measurement of DC current (as distinct from AC or PWM DC) are likely to be well beyond the reach of most of our DIY members; while accurate multimeters are ubiquitous; many of our members already own one, or can borrow one, or purchase one at minimal cost;

• under the conditions stated above (and I strongly disagree with Jaguar for recommending that ignition be turned ON/OFF once meter is in place ... why?), any device ... electronic throttle or otherwise ... that is drawing 10A quiescent is one very sick puppy (sorry, cat).

Finally, the point about rough indication of mV testing above fuses, is a real pearl. Having seen John raise this several times many months ago, I am sorry I overlooked it. The inherent fuse resistance will produce a small but measurable voltage drop. Often, very often, this can cut the time-consuming nature of diagnosis down to a very speedy elimination process.

Regards,
Ken

 

Thanks!!!!!
Super info!!!

 

I use a clamp on MA meter. It's a GTC CM100. About $130 new. I got mine used on EBay for about $80. It measures down to .001 MA. I had too much trouble trying to use a DVOM. Too much risk of blowing my good Fluke meter fuse!


Sheffield Research CM100 Test Equipment - Electronic Testing
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.
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I while back I got to work on a 2000 S V-6. with a current draw problem. Finally found a Jaguar document S414-02 High quiescent Drain - Install Forward Harness Bypass Lead. when I joined this forum there was a restriction of no posting docs. I also found a low drain from the sunroof that is stop gapped by pulling the fuse. Does anybody want to see this PDF?


Someone send me a PM as I can send the pdf and where.


Jeff
"S-Type is the only car I feel more beautiful after driving it!"

 

It's already on the site.

 

Only three years late, I wanted to throw in my 2 cents. Testing tiny drains with this method is frickin' awesome. There's no need to unplug any fuses or disturb the circuit. Once the car goes to sleep, this won't wake it back up again as with other methods.

I thought it wouldn't be very accurate, but I was pleasantly surprised. I rigged up a test circuit on my workbench (known amperage flow) and the results were spot on the money every time. This isn't a rough approximation of amperage. This method is HIGHLY accurate. I was able to reliably repeat the test results using three different meters: A high-end Fluke digital meter, a $7 HF digital meter/door stop, and an ancient Simpson 260 analog meter.

Here's a good description (with video) of the process:

https://us.autologic.com/news/testin...e-voltage-drop


Here are the best charts I've seen, print them out for reference:

https://www.powerprobe.com/fuse-voltage-drop-charts/

 

This site http://vestest.com/ has lots of good info but I can no longer see any about testing fuses.

 

I'm hoping cat_as_trophy can help here. I have a large drain 800-900 milleamps after 1 hour. ( S type r 2005, no non jaguar accessories ).
The FEM and REM are keeping the 4 switch system relays awake in the rear fuse box. Causing a flat battery over the course 4-7 days. If i remove these relays drain drops down to 40-50 millieamps ( slighty out of spec, but could be test equipment ?)
In one of your posts you mentioned a PATS sensor. I notice that when its dark, alarm disarmed, there is a glow from my PATS light which i don't think is normal?
can anyone confirm please.

Also after leaving the car overnight, often when i disarm the alarm, instead of the indicators flashing, the headlights flash. If i open the door ( remote does unlock the car) the alarm will go off. However if i press the remote a second time, the indicators flash and the alarm will not sound.

any ideas on this guy's. I'm currently reading through the battery drain threads, but have narrowed it down to FEM or REM keeping the relays active.
what colour relays do you have in the boot, the majority of mine are black in the boot, yellow under the bonnet .

 

Apologies for starting this thread again. I'm currently having the exact same issues with my 2005 S type. I've narrowed it down to a voltage drop across Fuse 33 (FEM, trunk switchpack, light dimming switchpack). I can only get the car to go to sleep after the prescribed 40 minutes removing Fuse 3. I have had the same symptoms you've had, flashing lights when opening, 4 relays energised permanently and was wondering what you did to resolve your fault?

 

Car will only go to sleep Fuse 33 removed, not fuse 3.

 

Unfortunately still not resolved.
FEM,REM and DDM all changed. I now park it near the window and charge the battery every few days.
When the weather is better i might do the fuse testing that's quoted above here.
Still following though as i don't like to be defeated by cars.

 

Thanks for getting back to me, same here, I have a battery isolation switch to fit as a last resort, but I wont let it beat me just yet. My next port of call this weekend is to disconnect the plugs at the bottom of the FEM one by one to try and narrow down the system causing the issue before swapping the FEM.

I'll let you know how I get on.

 

What i found with mine was that the FEM and REM keep the 4 relays energised by supplying a ground. This ground should disappear after approx 40mins when the car goes to sleep. Mine wasnt doing this.
But many things can keep the car awake.
Ign switch, door latch, anything on the CAN network.

the earth comes from the FEM and splices into the REM earth wire. Im thinking you could separate this wire and it might tell you which module is keeping the car awake.

Alarm sounder is also one to look at as it has a back up battery in it, ive disconnected mine in the testing process.

What i have noticed is that very randomly when the car is left my headlights and rear lights will flash as if the car is locking or unlocking. When i get to the car it is always as i have left it.

Anothet point to note is that apparently the cars wont go to sleep properly if the doors arent locked. Dont know how true this it.
Good luck. Keep us posted

 

I've had another day chasing the fault today. With plug CA31 disconnected from the FEM the car will go to sleep.

I have tested both front door latches for earth, with the passenger door, as soon as you shut it you get earth, not so with the driver's side. I suspect now that I have a faulty driver's door latch. CA31-8, 8-10 ohms resistance to earth with door closed. Open circuit (as expected) with the door open.

Disconnecting the plug doesn't make any difference to the car going to sleep as I think the drivers door module picks up on the plug being disconnected.

I might try disconnecting the door module now.

Moving the latch in and out makes a difference to the level of resistance, but there is still a resistance when there should be none to ground.

 

One pitfall is you can get it to sleep, but does it wake up when remotes are activated.

With some fuses out, it goes to sleep, but fails to wake up, therefore the remotes don't work.

 

with the plug disconnected surely it sees O/C so would think the door is open, hence it won't sleep ?

disconnecting the DDM, it will go to sleep, but you won't be able to unlock the car, so not sure it that tells you that it's that module ?

 

I'll order a door latch, which is the least of my problems now having got some plastic stuck in my ignition barrel. 🥴

It should see 0ohms, but the latch never gets to that. Might be why my lights sometimes flash on and off occasionally, and again when I open it.

I disconnected the door module but the car saw the door then as open, so it was pointless.

Next up Locksmith and a door latch, which, looking at the numbers ordered is a common problem.