From post #636 in this thread (holy crap, 636 posts!!! wow!):

So a little more info on this...the effected IS's must either have Blind Spot Monitor or Clearance Warning Sonar (or both) in order to be equipped with the Network Gateway ECU that causes this.
Dojoman is correct as there is an even newer ECU available. But if you have neither of these options, then the ECU is not causing your dead battery...which really isn't comforting either.

 

got my car back this time, they did not replace the ECU.

 

I can't believe a dealer could make such a stupid remark.
I recently started my 2016 IS350 (with BSM) after 7 weeks of inactivity due to an extended trip abroad - the car fired up with no problem.

 

Well they completely fixed something in the 2015s and newer. If I were getting the runaround from my dealer, it would be my last Lexus I purchased.

 

Well, there were at at least some here who insisted the problem never got fixed...

 

Has anyone replaced their battery with a OPTIMA YELLOW TOP? If so, what is the part number for the one you have?
I have a few auxiliaries which has lead me to believe is the reason for my dead battery...

 

Has anyone had the problem return after getting a new Gateway ECU and battery replaced by Lexus?

 

My car has BSM, but is 2016. Never any issues at all. So if this helps anyone--probably means Lexus did change something for 15+ MYs w/ BSM.

 

Mine was replaced ~12 months ago. I have had zero starting issues since replacement.

 

My 2014 also has BSM - never had battery issues (still have original battery) - it seems to be totally random. It also seems that they did figure what the issue was and made adjustments for 2015+.

 

I have BSM and have had the battery issue with my 2014 IS350 F Sport.
After reading about it, I decided to change out the battery for a more powerful Interstate AGM battery. I can leave the car parked for weeks now and it starts right up every time. The extra capacity may be hiding the problem with the ECU, but it's a non-issue as far as every day operation now.

 

At all times. However, I only use it for calls and texts, I never bluetooth music and never have (if that matters).

 

For Canadians, the American TSB for the Gateway ECU didn't apply to us despite having a VIN within the listed range (which I think is dumb), but I learned there's a TSB recently released for certain Canadian models now. I'm going to see if mine is included in the next service.

 

The TSB applies to ALL vehicles within the VIN range in North America. It's true that US and Canada will launch the TSB's independently because certain information needs to be changed for the specific region.
I.E. Miles is changed to Kilometers for the warranty period reference, the TSB number...and honestly that is usually the only changes.
The TSB calls for the vehicle to either have Sonar or BSM, or both, so that kinda leaves a lot of the Canadian vehicles out of the TSB because how many people bought the vehicle with either of those options.
Because the US has a wider variety of models available in the IS line-up, therefore there is a greater chance of running across a vehicle with either Sonar or BSM.

 

I just wanted to share my ongoing experience:

I took my 2014 IS250 F Sport with BSM into the Dealership in SoCal and they told me they narrowed down the battery drain to the Network Gateway ECU.

Since I have 65K miles, the dealer told me this part is not covered under my 50k Bumper to Bumper Warranty. They quoted me $8XX (Part + Labor).

With the help of this AWESOME forum, it seems like this issue is happening to other owners. Seems like this NG ECU is a defect and should be recalled. I contacted Lexus Customer Satisfaction and started a case with them and was told that a case manager will reach out to me within 2 business days. Updates will come as soon as I find out more information.

*OEM battery was replaced w/ a Lexus Battery 1-2 months ago directly from the dealership. Since the replacement, the car died four times.