Don, that is fantastic information, thanks. Whether that's the problem right now or not I feel confident I'll be doing that repair in the not too distant future.

I went out and tested my newly charged battery again this morning. 12.2 volts and 56% charge. Despite being told the battery is perfect I can't rule it out just yet. A parasitic drain is possible I suppose, but I think I'll take the car and have it tested with the battery installed. I think they can test the alternator etc. with their equipment.

Could this battery issue be the sole reason I am getting the suspension fault? I sure hope so...

 

I need some electrical help. I never really learned how to use a multi-meter, but of course I have one. haha.

I set it to read at the "200m" setting, which I presume is 200 milliamps? I don't know how to interpret my results though. I took out the trunk light fuse to remove that draw and then I waited about 5 minutes after I connected the multi-meter to allow the computer to go to sleep. The readings dropped from about 12.8 down to 10.4 and seemed to stabilize there. Is that 10.4 milliamps? If so, that's not much, right?

My red lead is connected to the 10A and black to COM. Dial is turned to 200M on the MA scale. Readings now (update) are around 9.93 (with a negative symbol "-" off to the left). If I put the fuse back in for the trunk light it jumps to about 26.0.

Can anybody read this post and tell me if I have a problem?

Thanks,

 

Hi Jeff,

I'm not sure how you have your meter connected or what you are trying to measure. In order to measure overall quiescent drain, you need to disconnect the negative battery cable and connect your meter between the negative cable and the negative battery post. You will need to set your meter on a high enough amperage range to withstand the initial current drain without blowing the internal fuse, so set the meter on 10A or 20A initially. You can turn it to a lower range as the systems go to sleep and the drain is reduced. Here are some TSBs that give you an idea of how to do this:

http://www.jagrepair.com/images/TSB/...%20Current.pdf

http://www.jagrepair.com/images/TSB/...nt%20Drain.pdf

https://www.google.com/url?sa=t&rct=...zfbrbIjmXt7PrQ

Cheers,

Don

 

Don you are very patient with me. I disconnected the negative battery terminal and put the multi-meter inline between the negative post and negative cable. I'm pretty sure I did the test properly I just don't trust my ability to interpret the results.

I had the battery tested today in the car, they again told me it was a perfectly good battery. They also tested the alternator and it passed. The guy said "it could be a bad cell, that wouldn't show up on these tests". I don't know batteries, but it seems a bad cell would be detectable, no?

I drove the car 30 miles last night and spent an hour running errands in town today; all with no error codes. Even though my equipment tells me the battery is low, it started fine and there were no codes. Last night however when she took my company car and left me her Jag, the suspension fault was constant. It sat for a few hours after she traded cars with me (I was at work) and since then I've seen no codes.

I'm rambling, lol. I would love to just buy another battery to rule it out, but the thought of spending $150 to replace a perfectly good battery makes me wince.

 

A good battery should show a voltage at rest above 12.2V typically.
If fully charged it's more in the 12.6-12.8V range after the initial rapid period of voltage drop.
When the engine is ignited, the readings are more in the 14V range because the alternator will charge the battery initially.

If a cell is damaged, you may have reading much below 12 V but then I doubt you could crank your engine.
There should also appear multiple warning lights on the dashboard because the electronic systems of the X350 are very sensitive to undervoltage.

If you have still a substantial current drain after the intial period following shutting down the engine (that can be measured with a multimeter as Don indicates), that may rapidly empty your battery, lower its voltge and eventually create all sorts of DTC's.

Back to possible culprits for your low suspensions signals, if the battery is in good shape, and now that you have changed your front shocks (and maybe after checking that the brass fittings on top don't leak), the likely causes may be the compressor seals as already mentioned or the valve block in the trunk.

 

Your alternator may have a bad diode, letting your battery drain overnight, but it will charge at the proper rate. Try unhooking the big fat wire on yours, & if it does not fail to start when you reconnect it in the morning, you have found your drain.Have ran into this problem more than once on older vehicles of many brands.

 

I will make a couple more comments on the battery because I don't feel this issue is resolved.

I have the exact same battery in my 2002 XJR. I tested it today and it showed 12.5 and 85% charged despite the fact that it's been driven very little lately. It sat for 6 days and was driven less than 20 miles yesterday, yet the battery seems good.

I tested my wife's 2004 XJ8 today after driving it almost 100 miles yesterday and it showed 12.2 and 63% charged. It can set for days and it doesn't drain any lower than that, but even after it's charged up within a short time after putting it back in service it settles at 12.2 and between 53% and 63% charged. This is of course while hooked to the car; both numbers go up if the battery is tested while fully disconnected from the car.

I know what you'll say, switch the "known good" battery from my XJR and see what happens. Smart idea, yes. I don't WANT to! haha. Everything is perfect on my XJR, I don't want to take the battery out.

 

Hey Jeff:

I'd be glad to bring my (Foxwell 501NT) scanner over - just give me a shout

And...the way you used your VOM was fine. 250 mA is OK (a typical parasitic drain). Bad alt diode is generally way higher

I sent you list of the Foxwell scanner Jag functions etc via PM

Sounds like you have eliminated the battery via swapping with a known good one

Not sure what you're using to get the "% charged" figures, but just charge the battery fully (with a charger), then read "% charged" again. If its much below, say, 95%, then the battery you're testing is probably bad. Just make sure your meter is set for (lead acid) starting battery. Deep cycle, AGM, etc batteries generally have a higher surface voltage. Most inexpensive "% charged" meters simply look at voltage. Best battery test is with timed load (eg carbon pile). But, batteries are weird...

The scanner should pull your Jag's "traction control" codes. I just went through similar goose chase with my (aging) M3. Bad wheel sensor harness

 

I assume you meant to say 25 mA? Here's a chart of typical Jaguar quiescent drains and shutdown periods by model:



This chart is from the attached document.

Cheers,

Don

 

Yes...woops...25mA (not 250 mA)

Interestingly, this figure (acceptable parasitic drain) keeps going up. My Mercedes wagon was ~ 100 mA, and within spec

Even a 250mA drain, given a 100Ah battery, would take a very long time to fully discharge things

 

Thanks for the offer hisport, I will take you up on it someday soon.

I gave in and bought a new battery. I thought the battery in the car was about two years old but when they read the code on it at the auto parts store they said it was 5 years old.

Before with the old battery, I could charge the battery to 100% and within a couple of hours of being in the car it would be down to 50-60% charged and 12.1 to 12.2 Volts. Ironically it wasn't causing any problems and the suspension code has not re-appeared in a couple hundred miles. On top of that the auto parts store was insisting that the battery passed all their tests and was fine.

With the new battery today, 12 hours after I installed it, the test results were 12.6 Volts and 90% charged. I really felt like I did the parasitic drain test properly and found nothing, so despite the fact I was assured the old battery was fine, I didn't trust it. It looks like maybe I was right.

As always if the story takes another twist I'll update.

 

Jeff,
Good that with the new battery everything seems in order.
Seems indeed that your previous battery was on its way out with malfunctioning cell(s).

 

While the battery was in need of replacing, it may not have been causing the suspension error. She said it happened again today. No drivability problems, just the error.

Hisport, I guess I will be trying to get together with you soon. I'll buy lunch!

 

It's confirmed that the old battery was bad. With the new battery the Volts are always 12.5 or above and the % charge is excellent. I tested again after the car was parked for about 16 hours and the readings were exactly the same, so no parasitic drain. The other battery would drop rapidly to 12.0 volts and then continue to sink on % of charge readings.