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I have a 2015 Highlander. The vehicle has a slow battery drain. I have read many of the posts on this forum and I knew going in that these issues can be difficult to isolate. I took the vehicle to my local shop that does my normal maintenance. They tried to isolate the problem and think that it might be one of the door switches not remaining shutting off all the way so there is discharge.

Does anyone have experience with taking such a problem to Toyota? Do they have special equipment to help isolate the problem? When you get work done there I know it can be costly. I fixed a problem with my radio/nav system dashboard rebooting on its own. I found a link on this forum, downloaded some software, plugged the thumb drive into my Toyota and updated the system. Saved hundreds I think. I may have to go to Toyota as a last resort. Experiences that you have had will be very helpful. Thanks in advance.
 

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Is the door switch working or not? You multi-funtion display should show if any of the door is not closed (via the door switch with an open circuit or not)? Also, if any of the door switch is not working (meaning keeping the circuit closed) then the dome light should remained On 10-15 seconds after you supposedly shut all of the doors and liftgate.
 

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I've seen numerous alternator diode sets fail, as in one (or more )diodes decides to 'Conduct just a little' when it shouldn't. The fool proof method to isolate involves disconnecting the large positive wire on the alternator. Something that isn't so easy to do these days. Toyota should have a tester machine that they can check for full power off isolation with the alternator OUT of the vehicle.
 

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If you decide to remove the large Pos + cable from the alternator, be very careful not to ground (touch anything metal) with your wrench. It can be very exciting and dangerous. It is always "hot" until you disconnect the battery from the system.

Not sure with your 2015 but with my 2017, when any electrical loads are left on once the engine has shut down, one or more of the control modules will shut down whatever it is that is still on such as interior lights, radio. I've found a door ajar for days many times but no battery drain after a few minutes. This would seem to point to something other than a door switch type of issue.
 

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Genec...yeah, trying to finds whats drawing down your batt. can be a tedious/frustrating job or maybe not? If not already done, may need to do test using amp meter..pulling each fuse one at a time & watching for v. fluctuation. Rusty mem, so don't quote me. lol! Also try goog for info, might even be utube DIY. Good luck on outcome.
 

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So, did you replace your battery yet?

 

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Discussion Starter #7
So, did you replace your battery yet?

Yes and it hasn't happened since then but I haven't let the car sit for a day or 2. That's when it's been a problem in the past.
 

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You don't say how large your parasitic draw is, but a member here, Delphi51 found this "I happened to turn the headlight setting from auto to off while the clampmeter was in place and noticed that the drain dropped to a quarter of an amp. Next morning battery voltage was 12.6 volts! My guess is the auto headlight feature requires the computer to be actively checking for daylight and it’s the computer that wastes the quarter amp, maybe more at times."
It was from this thread Does Gen 3 Highlander have a "Smart " Alternator?

I've since got in the habit of turning the headlight switch from auto to off when the vehicle is parked, and plug in my battery tender if it sits for more then a few days during the winter months.
 

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Glad to hear that was in the past. My 2016 HL still has its OEM battery today; for the past years, I have parked this HL for 2-3 weeks at a time for many times during my personal/business trips, each time when I return (I am sure during those times, the battery although getting weak) always starts right up without any issue. The one thing I alway do before the storage was to make sure the battery was fully charged (no, I do not disconnect any of the battery terminal during storage).
 

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I have a 2015 Highlander. The vehicle has a slow battery drain. I have read many of the posts on this forum and I knew going in that these issues can be difficult to isolate. I took the vehicle to my local shop that does my normal maintenance. They tried to isolate the problem and think that it might be one of the door switches not remaining shutting off all the way so there is discharge.

Does anyone have experience with taking such a problem to Toyota? Do they have special equipment to help isolate the problem? When you get work done there I know it can be costly. I fixed a problem with my radio/nav system dashboard rebooting on its own. I found a link on this forum, downloaded some software, plugged the thumb drive into my Toyota and updated the system. Saved hundreds I think. I may have to go to Toyota as a last resort. Experiences that you have had will be very helpful. Thanks in advance.
Do you have that link by chance?
I’ve got same issue with radio/nav system in my 2015 HL XLE (reboots randomly while driving). I’d like to try the downloadable update!!
 

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Discussion Starter #12
Sorry but I don't. If you search for stuff like Radio reboot, or upgrade navigation system you should find it.
 

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I have a 2015 Highlander. The vehicle has a slow battery drain. I have read many of the posts on this forum and I knew going in that these issues can be difficult to isolate. I took the vehicle to my local shop that does my normal maintenance. They tried to isolate the problem and think that it might be one of the door switches not remaining shutting off all the way so there is discharge.

Does anyone have experience with taking such a problem to Toyota? Do they have special equipment to help isolate the problem? When you get work done there I know it can be costly. I fixed a problem with my radio/nav system dashboard rebooting on its own. I found a link on this forum, downloaded some software, plugged the thumb drive into my Toyota and updated the system. Saved hundreds I think. I may have to go to Toyota as a last resort. Experiences that you have had will be very helpful. Thanks in advance.
I had a very similar problem with my 2nd Gen Highlander. I chewed through two batteries over one calendar year due to this neverending battery drain issue. Finally, my private mechanic got a line on a very good mechanic specializing in electrical system problems. I went to them, they had my Highlander two days, and discovered the problem was the A/C clutch relay was faulty, causing the A/C clutch to constantly engage/disengage even when the engine was turned off. Relay replaced, problem solved. :)

Not saying this is your issue, but obviously one possibility to eliminate.
 

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I have a 2015 Highlander. The vehicle has a slow battery drain. I have read many of the posts on this forum and I knew going in that these issues can be difficult to isolate. I took the vehicle to my local shop that does my normal maintenance. They tried to isolate the problem and think that it might be one of the door switches not remaining shutting off all the way so there is discharge.

Does anyone have experience with taking such a problem to Toyota? Do they have special equipment to help isolate the problem? When you get work done there I know it can be costly. I fixed a problem with my radio/nav system dashboard rebooting on its own. I found a link on this forum, downloaded some software, plugged the thumb drive into my Toyota and updated the system. Saved hundreds I think. I may have to go to Toyota as a last resort. Experiences that you have had will be very helpful. Thanks in advance.
Some good videos out there for checking for a parasite drain. The old way of pulling fuses no longer works on newer vehicles because of all the computers. Basically with computers sleeping check for a current draw ( all doors closed and hood switch bypassed if present too). If draw is excessive the measure across fuses looking for any voltage. If any voltage if found determine if that is all the draw or only particial. .
 

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I have a 2015 Highlander. The vehicle has a slow battery drain. I have read many of the posts on this forum and I knew going in that these issues can be difficult to isolate. I took the vehicle to my local shop that does my normal maintenance. They tried to isolate the problem and think that it might be one of the door switches not remaining shutting off all the way so there is discharge.

Does anyone have experience with taking such a problem to Toyota? Do they have special equipment to help isolate the problem? When you get work done there I know it can be costly. I fixed a problem with my radio/nav system dashboard rebooting on its own. I found a link on this forum, downloaded some software, plugged the thumb drive into my Toyota and updated the system. Saved hundreds I think. I may have to go to Toyota as a last resort. Experiences that you have had will be very helpful. Thanks in advance.
Good read here.\> Parasitic current on a 2004 Sienna Good to know that 1/4 amp draw drops to 12 ma in a few minutes.
 

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I've seen numerous alternator diode sets fail, as in one (or more )diodes decides to 'Conduct just a little' when it shouldn't. The fool proof method to isolate involves disconnecting the large positive wire on the alternator. Something that isn't so easy to do these days. Toyota should have a tester machine that they can check for full power off isolation with the alternator OUT of the vehicle.
If it's an alternator diode that's bad...then checking voltage at the battery when engine is at high idle should be enough of a test. Voltage should be between 13.7 and 14.7.

Any decent mechanic (dealer or independent) will have the proper equipment to isolate a drain.
 

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I have a 2015 Highlander. The vehicle has a slow battery drain. I have read many of the posts on this forum and I knew going in that these issues can be difficult to isolate. I took the vehicle to my local shop that does my normal maintenance. They tried to isolate the problem and think that it might be one of the door switches not remaining shutting off all the way so there is discharge.

Does anyone have experience with taking such a problem to Toyota? Do they have special equipment to help isolate the problem? When you get work done there I know it can be costly. I fixed a problem with my radio/nav system dashboard rebooting on its own. I found a link on this forum, downloaded some software, plugged the thumb drive into my Toyota and updated the system. Saved hundreds I think. I may have to go to Toyota as a last resort. Experiences that you have had will be very helpful. Thanks in advance.
Glad for you the update to enTune solved your rebooting issues. Did not for us and dealer ended up replacing the unit. No troubles since, thankfully. Relating to battery drain, I do have issues with the control button placement over the rear view mirror. We are constantly turning on a map light or disabling the interior lights by mistake while trying to open the garage door. And if the kids or someone in the back seat have already opened a door we don’t notice our mistake until we look outside and see the interior lights still on long after exiting the vehicle. Luckily we have always caught it so far and corrected the mistake so have not drained the battery yet.
 
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