ThinlaneT

Since I bought the car (October 2017) it probably already had the issue (seller didn't tell me about it), but experienced no signs of it as I drove at least 2x 50 miles, 4 times a week, keeping the battery fit enough. I once left the trunk open over a night during a cold winter night. Although I think the GS shuts the tailgate light after 15 or 30 minutes, the battery was dead enough to only trigger the starting relais, somehow. Soon after that cold winter the battery finally died in march 2018, 2,5 years old. As the car came from the east-side of the Netherlands, which have colder winters than where I live, mixed by the fact the previous owner only drove short trips with it, the battery was probably already passing away for a while. I checked most of the cables by eye for damage but couldn't see anything in kind of damage or wear. The only thing is, when the dampers of the tailgate were a bit old and loose, some friends slammed the tailgate pretty hard, forgot that I said it had auto/soft-close... That's why I'm guessing the tailgate lock as cause of the drain, as it since then, unlocks itself 4 or 5 times when opening the boot by the button on the boot. No damaged occured when I got the car. Still driving lovely, once it drives... Checked the ground-cable from the battery to the chassis (which sometimes get rusty as it is in a quite humid and dirty environoment), but is was nice and clean.

Thanks @Mihanicos. The battery is new since January this year. Didn't start the car when it was below 12.35 Volts and if not driven I put it on the charger weekly (also due to the cold weather this February). Alternator and rectifier are working in good order. Tested the drain on it in October; no drain on that part. Even tested AC voltage over the battery (as a bad Alternator will have some current running back). Alternator charges (14.2V at cold start, later 13.9/13.8V when "warm"). I have a 70amp/hour battery. To my knowledge the practical capacity of a fully charged battery is 70% (as on less than 30% of the battery the motor probably won't crank and it definetly will damage the battery if you do so) * 70Ah = 49Ah -> 49 / 65mAh = 754 hours = 31 days till the battery should be "dead". As I notice some voltage drops on those 2 minute intervals my monitor registers; the average drain is probably a lot higher. I noticed on the Amp meter some peak drain of 300mA for a couple of seconds, but without a proper scope I can't have a say on the actual average drain. As I follow the trend my battery is dead within 15/16 days so the actual drain would probably around 130mAh.

I pulled the fuse (found it, although some information said also the fuse for the filler-cap controls the tailgate). It won't open now so I suggest it excluded. My rubber is still soft. Lets find out if it reduces the drain.

That's an interesting thing which reminds me the lock unlocks itself multiple times when I press the button (rubber cover) and pull the trunklit open. I think it never unlocks itself once, just 3 or 4 times. Does that sound familiar? I was already looking for the tailgate lock fuse, but didn't found any.

Good to hear it was the exhaust. I got a P0138 fault code (Check VSC lights) but my ECU seems to have dementia as it seems the Check VCS warning has gone . I thought these lights were triggered by what was registered in the ECU. After humid days or rain, the fault comes up again. Already checked once at the Toyota dealership quickly but it doesn't seems to be the Labda sensor, as it still sending values/pulse. I do have the first of the batch Mk3 GS300's which was told me the ECU of them have some narrower massure/thresholds on the exhaust values. At next service run/MoT I'll let them check the exhaust system.

Well, I reached for some help in this quest. Late December I had bought a Battery Monitor 2 of VPM to monitor the voltage on the battery via Bluetooth and an app. Monitor itself registers each 2 minutes the voltage level, using 1mA. The voltage drop was still significant after the car being recharged (via charger or driving around for 45 minutes, highway mainly). As I've probably try to start the car in the past when the battery was too low, I may have damage the battery so I decided to replace the battery with an new one (Optifit Toyota OEM). I charged the battery before replacing it with the old one. Sadly after keeping up the same weekly activity of driving around for 35 miles or putting it on the charger, I noticed no difference in the voltage drop by the battery monitor as with the old battery. It dies slowly within approx 2-3 weeks (but I don't let it come that far as it damages the battery). Looking at the daily graph the degradation isn't a solid/fluid line, but got some drops in it, telling me that there is still some activity going on. When putting the multimeter in series, I measured 1.2A after locking, after 1 minute 900mA, after another minute 375mA, followed by 175mA after another minute and keeping up 1 hour and 4 minutes till going to 65mA. I found a fellow '08 GS300 owner which had the same pattern, but experience that the 175mA to 60mA drop was only taking a few minutes. He is using a dashcam (which goes into stand-by) where I don't have any additional/aftermarket stuff. He didn't have that "crusty" line in his voltage degradation (he's using the same monitor as mine). Pulling the following known problametic fuses didn't effected the score: - Radio fuses (3) - Tilt & Telescope Steeringwheel fuse - Cigarette lighter fuse - FR and RR doorfuses ( as I noticed that the door didn't unlock once or twice) So bottomline, I'm stilling having that anoying draw, caused by 1 hour of 115mA above "normal" drain and some activities after an hour. I was also thinking about some can-bus issue, as I am thinking that the GS draining more after a drive than once put the multimeter in series (and therefor need to cut the circuit). It's not based on hard evidence, just the output of the clamp-amp meter (although I doubt the proper reading of it).

Ok, I’ll have a go tomorrow. One other thing that came up that I have a P0138 fault code, which is the 2nd bank lambda, only occurs after it had rained or it is moist (like a autumn morning). During periods of fairly clear weather, the fault code dissapears. Maybe the harnas of the sensor(wire) has been damaged were humidity effects the faultyness. I suppose that’s only engaged when the engine is on so no draw there. I might also check the alternator for it’s diode. Its still the original alternator I believe.

I ditched all the after market stuff (I use the bluetooth phone thing integrated in the radio/satnav unit) and I put the key away (more than 15 feet). Proximity of the keyless entry is only 5 feet around the drivers door/passenger door

Thank you Herbie, I'll check how I can disconnect the interior radar. Altough when fully locked, I expected the alarm go off when it was active and I was in. Fore the doors, I pushed the pin-switch mechanism with some clambs tot mimic closed doors. Internal lights go off when performing that (as well as the light on the dash). I also put the key-fob away not to trick the proximity sensor for the key. For the rest, I doubt it matters if you lock or unlock the car. When locking, well some systems go to sleep, but also actives alarm and interior radar and so on. Therefor I checked first without locking, I also locked it and tested again. No difference. I think the problem here is that I can't find the location of the draw, but I think I can concluded there is a draw afterall. I find it hard to believe that the draw can't be spotted after let say 30 minutes. But maybe I'm thinking a bit simplistic here. I didn't start the car before though, It's just standing there for a couple of weeks now, putting a charger on it, once a week. Maybe I'll need to spent some on the fuses with test-points and even more patience. As there are 5 fuse boxes, you don't know exactly if all measures are done to mimic all the systems and taking two hours waiting (and start over again if something is interrupted) it's a pretty "draining" job...

Hello, Since Corona-times, my '05 3rd gen GS300 President doesn't get much miles anymore, working almost only from home. I encouraged myself to just drive at least a trip of 30 miles every 1 or two weeks with some highway miles to charge the battery. Sadly there was a parasitic (unknown) draw going on, which killed my 2,5 year-ish Toyota battery in June this year, probably when trying to start and the battery % was eventually almost too low. I bought a 80Ah Tokohama Asia battery and worked fine. As the draw from this battery was also noticable (after two weeks the battery was flat) I went searching for the parasitic draw. Unhooked the minus-pole and put the multi-meter in serial, I measured a 0.9A draw short after closing the car, 0,37A draw the first 5 minutes after that a 0.17A draw. I also checked after half hour, hour and two hours, but it remained 0.17A. I tried pulling the fuses one time after eachother, but no effect. After being cramped in both footwells and baggage compartment for the fuses, I might have missed one, but I didn't found the fuse that may drop the expected/normal 0.05A draw. For now I don't have a clue. I removed all the aftermarket stuff (Stinger from previous owner and OBD2 BT device (which I was lost), but no effect. I found in the other fora (as well the IS250 one as I guess they share some electronics), that the MB-X circuit fuse might a source for a draw, together with the Claxon/horn (back-up battery) and also the steering column (when somehow miss-alligned the motor want to reposition, allthough I can't hear any motor or movement). I will check the fuses again. One thing that was interesting, was that when pulling the fuse of DC Cut when in the 0.37A draw moment, the draw dropped to 0.17 inmediately. I found that the method of pulling fuses is somehow questionable as other circuits may takeover the function so a draw like this will be terrible/impossible to find. Do you have suggestions where to find any draw from experiences in the past?