Problems With Battery Discharge On My 98 Ls400

[sambo_jones]

I just bought my 98 ls400 about 3 months ago and it's an absolutely fantastic car except that about a 6 weeks ago the battery started to randomly discharge. And by random I mean it'll be fine for a few weeks then i'll go to sleep one night and it just won't start. Another thing that is wierd is that sometimes it i just need to crank it 4-5 times to get it to start and sometimes no matter how many times i crank it it seems totally dead. I always make sure that all the lights are turned off before i leave it sitting. Another wierd thing is that it seems to go dead faster if I leave the stereo on when I turn it off, but if I turn the stereo off first it seems to last a little longer. This is getting to be pretty dang annoying and was hoping that one of yall might have heard something like this before. Also the battery is brand new.

edit: also a tailamp failure warning came on about 5 days ago not sure if its related but all my lights work properly so not sure what thats about

[SKperformance]

Try this,

Before turning off the car move the dome light switch over to "OFF" not "door ".

I also have a slight drain on my 98 LS and after replacing the interior bulbs i found that the dome light is being kept running all the time.It is not enough to produce any light but enough that when i look at the bulb it shows a glimmer of light.

It has gotten much better since i did this but i still have to track down the rest of the draw.

Also make sure you don;t leave the headlights in auto as it sometimes will not shut down completely.

[sambo_jones]

Thanks I don't leave my headlights on auto, but i'll try turning off the dome switch hope it works. Any idea on how to track this battery draining down?

[SKperformance]

You need a amp meter

disconnect one side of the battery and connect it in series to the pole.

Note the draw on the battery with everything off.

Then slowly disconnect fuses to see which circuit has the abnormal current leakage.

[sambo_jones]

Thanks I appreciate the feedback I'll see if I can figure it out, I'll post results if I find any incase anyone else has similar problems.

[fabphil]

I reopen this topic because the battery of my LS400 98 gets discharged if I don't run the car for about 10 days.

I measured the drain about 0.4V (7 V through 22 Ohm) which is a lot (10Ah/day, 100Ah/10days ok).

I tried to locate the draw by removing each (small) fuse one after the other -> no success. I have also disconnect without success one after the other the cable connections of the fusible Link Block close to Engine Room J/B..

As far understand the Body Ecu circuit is the only suspect which remains and indeed it is active when switched off.

So the next test is to disconnect the Body Ecu.

Hmm, it is located behind the Instrument Panel J/B (left foot driver). I would appreciate your feed back: Is that ecu easy to remove?, Have you experienced such a drain?.

Behind this issue, every system of this car works alright. I have cleared the the side of the butterfly throttle, I did not replace the throttle gasket because the one I bought from Lexus was not the good one (no much play to take this throttle body out). I have checked the spark plug. They are Denso Iridium, probably genuine from the factory (the car is 150 mkm), with the gap still at 1.1 mm. Replacement is to be done at 150mkm or when the gap is 1.2mm.

[curiousB]

7 V across 22Ω resistor is 318mA which is very excessive key off current. You want to be down under 50mA. You should read 1.1V or less across the resistor.

If you have tried all the fuses maybe the alternator is at fault try the procedure here:

http://us.lexusownersclub.com/forums/topic/75789-1999-ls400-and-obd2/?p=461626