My battery used to die after sitting for a day or two. I brought it into the dealership a few times and they mentioned the battery and charging system were healthy.

I narrowed the issue down to me using an air compressor a few weeks back to pump up a slow tire leak. Even tho I had the car running while using the air compressor, the battery would die after not having driven the car in over 20 hours (which didn't happen often since I drive my car to work everyday). This has happened on two separate occasions and the time in between myself using the air compressor and the car dying has varied between a few weeks to a couple of months.

I have since gotten a booster pack with a built in air compressor and have not had a problem since. It's worth mentioning I have a few aftermarket led's mounted into my front and rear bumper that I keep on for car shows for over 10 hours straight and the battery seems to be holding up ok.

Not sure if this applied to your situation but I hope you can find something a solution soon.

 

The car goes to the dealership this week (again). I will make sure it is captured in the records. Regarding the use of other equipment or modifications to drain the battery there are none. I will keep you all posted. I have to make sure they put it in their records.

 

My dealership found my problem easier. 2014 IS250 F Sport

In the service record they wrote "REPLACED OPEN CIRCUIT GATEWAY ECU REPLACE GAEWAY ECU - OPEN CIRCUIT IN GATEWAY ECU - FOUND GATEWAY ECU CAUSING UNWANTED BATTERY DRAW. GATEWAY ECU WAS REPLACED WITH UPDATED VERSION."

Hope that helps!

 

My dealership just replaced the battery.

I tried to start up my car saturday morning and the car was completely dead. Jumped started it and went to autozone to check the battery they said it was fine. Then he checked the alternator with his machine and said it was an alternator failure. Went to Lexus and they just gave me a new battery saying the battery was bad.

"perform battery, starter, and charging test. -- battery failed test. -- replace battery"
part number
LEX 00544-MF240-575

 

Thanks 949FSport. Took 2014 IS350 to dealership due to repeated dead battery. The result: Gateway ECU issue. We showed them this note on how you had this issue. They gave us a loaner for 6 days because they have to order a part and contact Lexus Specialist

 

Thank you 949FSport. To car to dealership today and the result: FOUND GATEWAY ECU CAUSING UNWANTED BATTERY DRAW. We showed them this note from the forum thread. They gave us a loaner for 6 days because they have to get a part and have the Lexus Specialist present for the repair. Something is up ???

 

Is there enough conclusive evidence that the GATEWAY ECU has been the majority of the problem for most people? My Lexus Dealer said there was nothing wrong with my 2014 IS 350 AWD. Battery was in good health and no significant amount of parasitic drawl.

I bought a battery tender and a lithium-ion compact jump starter for the car. Lexus Corp was suppose to send me $100 check to buy the battery tender but I never received it. Could be my bad on that part for not checking up. Oh well, life goes on I guess.

 

The manager of service department said he had to go through more red tape n signatures to get the part to correct the issue with battery drain. It took 3 stops at the dealer over a years time to get them to admit a battery drain problem. Be persistent!

 

This also happened to my 2014 IS250 F Sport. It sat in my garage for about 2 or 3 days and the battery died. I got it checked at O'Reilly's and they said the battery was ok but there was something wrong with the alternator. So I took it to the Lexus dealership and they kept it overnight. They said the battery and alternator tested good and they just recharged the battery....
The following week I left it in my garage for 2 or 3 days again and it started just fine... I'm going to try to leave it alone for maybe 4 or 5 days and see if the battery dies again..

 

My battery got replaced a year and a half ago and no issues until yesterday, car was dead after it sat for just two days in the driveway.

 

can't believe this is still happening after almost 3 years. I'm glad i never experienced this

 

Well, I got some good news today. After reaching out to my my Service Manager over email last night about the issue, his SA called me this morning to tell me they are aware of the issue and that they put in the order for a new ECU. No checking the car out again and running tests. A simple email was all it took.

They should get the ECU in a few days and I'll book an appointment soon after.

In short for anyone else who might have the battery drain issue, don't waste anymore time on troubleshooting the alternator, replacing batteries etc since Lexus seems to now be aware of the permanent fix. And if your dealer is not, point them to this thread.

 

CorradoMR2,

Glad you have a new ECU for your 3IS. Hope your battery still looks okay. In my case, my dealership first replaced the ECU in my IS in January 2016 and then the battery finally died after 2 months (March). But the bonus is the battery they replaced somehow has much higher CCA.

The day when I took back the car after a new battery was installed, the reading from my battery tester was 1042CCA. Then the battery was sitting idle for the whole night, it was 1031 CCA when tested again. The rated CCA on the new battery is 575CCA. I didn't believe it was accurate but didn't bother to check it again as everything looked fine.

Last week after I got back the car from service, it came to a surprise that the battery has 1001 CCA.

 

AndyL, to be clear, your original battery still drained after the new ECU?


I got my ECU replaced last Friday and hoping the battery will not drain again...

 

I don't think the original battery continued to be drained even after the ECU replacemen. The simple fact was the original battery finally died even with the ECU replaced. I guess what happened was the original battery was beaten up by the draining issue for too long. Actually when the dealership replaced the ECU, the battery seemed to be still okay but I got the feeling that the battery should have been replaced at the same time. However, their diagnostic still showed the battery in acceptable condition and i couldn't argue with them.