salimshah

What was the range of the parasitic draw?
First turn every auto feature off and turn off everything. vanity mirror-light, glove compartment etc should be off.Hood needs to be closed too [tanti-theft has a circuit into the hood open] .Remove the keys, lock the doors. The draw should step down in time and after about 15 mins or so it should read between 150ma - 350ma [not published but a range I have seen members post]. It never goes down to zero.

Salim

debor300

Salim,
I was using the 10 amp setting on the voltage meter. It would start at 80 drop to 50 after a few minutes and before I removed the fuses, one at a time. All doors were shut and the key out of range. The CD player makes noise but I don't see what fuse that is to deactivate. When I got to fuses 15 and 16 the drop was greater (around 25) but when both were out the meter went to zero on the 10 amp setting. the mechanic looked up the wiring diagrams for the two fuses and found a common part. I don't know what setting he used but I feel confident he troubleshooted the issue to determine the "computer multiplex network body" is the issue. Now where to find the part. Not sure about using ebay. I found the part on another website but wondering how legit these site are. the part is expensive. I am open to suggestions on where to purchase the part.

Debo

salimshah

I am lost with numbers without units. It definitely can not be 80Amps. Was it 8Amps or 800mAmps, The mAmps would make the most sense. If it is 500mA, you are a tad bit higher, A good battery should be able to sustain it for 10-15 days.

Sorry cant suggest where to but the part from. LKQ usually has Lexus parts.

Also check what other things the part controls. If it is the main ECU, you would need master keys and a way to enter current odo value.

Sakim

Mauser

On years 1999-2002 the main ecu doesn't store mileage, it is written to an eeprom in the instrument cluster. The ecu on these years can be swapped fairly easily. Just need to flash the immobilizer eeprom.

SVRX300

Years ago my clamp meter showed the standby current draw is 70 mA. Two weeks ago my 2000 RX300 had a battery dischaged to about 2.7V for the first time during 16 years of service. After jump start and normal drive, no unexpected discharge again so far. I re-tested the standby current and it is still 70 mA. Battery from Costco is two years old

I hope it's a one time glitch.

ljgib56

my situation is a very dead short, you can see the voltage drop on a multimeter like a clock counting down, Battery appears to be fine.

Australian

Might sound mad but my cd stacker never stops key out etc disc stuck in changer dash changer not glovebox it randomly attempts to change discs I am certain this has been responsible for my flat batteries over time.

dugoram

I am experiencing the same issue with my 2001 RX300. I replaced battery about 6 months ago and recently the alt belt. Now my daughter's 2014 RAV4 is having the same issue. One common denominator...both have Interstate batteries from Cosco. Still doesnt make sense as they run fine and on rainy days they seem to have battery issues.

bobinyelm

First, while I seldom think there are baseless coincidences, I would seriously (seriously) doubt that the Interstate batteries are at fault.

Run the parasitic drain tests I see referenced above, but even before you do that, why not just disconnect one of the car's batteries and make sure that it stays charged when not connected to the vehicle. A well-charged battery should not decrease below about 12.25 volts when not connected to any load. See this chart to determine your battery charge: https://electronics.stackexchange.co...rge-percentage

Remember to find your radio code if you have a code radio, and realize it will reset your OBD II computer so you can not have the car emission tested until all of the Readiness Monitors have been reset by completing the required number of Drive Cycles.

It can be very frustrating trying to find a small parasitic drain, but don't give up!

You can purchase a battery trickle charger for about $10 from Harbor Freight (on sale or with Coupon) that you can use until you figure out the problem, of course.
https://www.harborfreight.com/search...ckle%20charger

dugoram

Thanks...I have a trickle charger and have taken the battery out to test how long it will hold a charge. I recently installed a rebuilt starter and wonder if it can drain a battery if it has a short of some defect. When I connected jumper cables I could hear a buzzing sound coming from the area of the starter. The reminded me that I had just changed that a month earlier. When I replaced my battery I now receive p1130 and p1150 codes that I did not receive earlier. Thanks again for the help.

DrainBrain

I have a 2000 RX300 that had a parasitic battery drain which was tracked down to the computers not going to sleep. After practically disassembling the entire dashboard, door panels and fuse boxes in order to track the drain to the specific module, or component we came up empty. After extensive research and discussions with Master Lexus technicians, I finally figured it out. What kills me is that everyone on these blogs all have opinions, but no one has come up with the solution and it’s an incredibly common issue, according to my local Lexus service manager with 30 years under his belt. My problem stared out intermittently. Sometimes we didn’t drive for a week and she fired right up in the dead of winter. Other times we would park it at night and come out in the morning to a flat dead battery. At the same time, my window switches on the driver’s door were starting to act up. Not relating the switch issue to the drain, I ordered a Chinese knock off from eBay so I wouldn’t get caught with my window frozen in the down position. Problem solved, but now my battery drain was constant. As we ruled out different systems we noted an amp draw if we opened any of the doors, hatch, or hood, except for the driver’s door.

so here’s the deal: the computers will only sleep if they get a signal that the doors are all closed and locked, hence the irritating auto lock routine. Because the drivers door wasn’t sending a close signal the computers stayed lit up. After my discussion with the Lexus tech, I was informed that the drivers window control is actually the main courtesy lighting module and that they have had a lot of problems with them. Based on that, I decided to try one last ditch effort before installing a battery shutoff switch and ordered an OEM switch from an eBay salvage dealer. Shazam! All problems corrected. This is the same stupid system used on many different Lexus models of this vintage. This has been a long expensive and incredibly frustrating journey for this lifelong Motörhead. I hope my story and ultimate fix helps others avoid the pitfalls of this electrical nightmare. KC

maxSteel

But if it thinks a door is open wouldn't the courtesy lights stay on?

DrainBrain

You would think so! The fact of the matter is, the dome-light would light up, but the light at the bottom of the door panel would not. A totally convoluted system. All I can say is that I spent a lot of time along with a retired ASE master technician with multiple electrical certifications and couldn’t figure it out. We put the OEM door switch in and the problem is gone. Also the little light at the bottom of the door panel lights up again. I can’t speak Japanese and I certainly can’t think in Japanese terms when it comes to these systems. But my explanation is the fact of the matter. Do your own research, focusing in on that door switch module.

Nad1370

^^^
I believe its called a Multiplex communication system. (not a Japanese term)
Their mother brain is the Body ECU.
My bro had a similar problem with his 03RX.
He needed a window master switch (drivers)
I couldnt understand why the door panel light went out when i disconnected the switch.
Apparently that window switch, also called the drivers door ECU, controls the light.

Although if i did have a parasitic draw, id start pulling fuses out first.
Then connectors.
I'm sure your master tech did this and he wouldve seen a change once he pulled that fuse for the Front left door.
Or did he?
Either way, glad you fixed your issue.

DrainBrain

Yes, I did all of that before I brought him into the picture. However, there are multiple systems that run through the two circuits in question, hence the necessity for pulling the car apart to start unplugging each of those systems with no joy. It’s a dumb, or maybe not so dumb system to get you to bring your car to the dealer and spend more than the car is worth in diagnostic charges. I’m thankful my local Lexus dealer put me in touch with the old timer service manager that took the time on the phone to point me in the right direction...