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'16 Toyota Highlander starts by itself

MT Madman

New Member
My wife's 2016 Highlander Limited has started by itself on several occasions, I've never experienced but then I rarely drive it. My wife will go into a store shopping and come out with it running, she has no idea how long it's been running. We've taken it to the dealer but of course they can't replicate the problem and that's as far as it goes but this will be our last Toyotas (I drive a '15 Tundra).

Oh I should add; it doesn't have remote start either.
 

kennythewelder

Super Moderator
Staff member
100 Posts
Something is tripping the BCM to do this. Be it a signal from another remote start key fob, a signal from an out side source is causing this, or its an issue with the BCM itself. Just because you dont have remote start, I bet the info for that is in the BCM. Does this just happen in one place its parked, or does it happen in many places. Is there another dealer close to you? Maybe try another dealer. Have them read the BCM, and see if there are any issues with it. Or ask them if the BCM could be the issue. IMO, thats where your problem and fix is.
 

toyotafan

Toyota Truck Club Founder
Staff member
1000 Posts
When it's running is anything else amiss? That is, when puts the key in, does it shut off? Does unlocking shut it off?
 

MT Madman

New Member
It's not a remote start so shouldn't be an issue. It has the keyless entry and push start/stop, if fact the most recent time my wife was sitting in the car after just shutting it off.
 

kennythewelder

Super Moderator
Staff member
100 Posts
It doesnt matter that its not a remote start. The info to start the truck, is in the BCM. Once you turn the key, it sends a signal to the BCM. Then the BCM has a program in it, that starts the engine through a relay. In the old days, you turned the key, and that closed a relay, and this engauged the starter, but that is all done by the BCM today. Also the BCM has to get a signal from the key before it will let the engine start. That is why there is a chip in you key. The programming may very well be in the BCM for remote start even though you dont have it. Toyota is very protective over there programing on there BCM, and ECM. If the engine is starting and running without the key, then that is the program for remote start, and that is in the BCM.
 

toyotafan

Toyota Truck Club Founder
Staff member
1000 Posts
That's why I was asking if it turns off when you put the key in the ignition and/or unlock the doors. If it does, then it's getting a signal somehow to start the truck. If not, then you have a short and closed ignition circuit somewhere possibly. I had a '62 GMC that had a water leak in the cowl that would short out the starter / ignition connection coming out from the dash to under the hood. Freaked me out when it started on it's own once. That's clearly not the same thing, but it goes to show the water closed the connection.
 

toyotafan

Toyota Truck Club Founder
Staff member
1000 Posts
I've done a bit of reading on this @MT Madman ... have there been any other upgrades to the vehicle that tie into the electrical system at all? Any radio or navigation system updates, aftermarket alarm?
 

MuddyTacoma

Mechanic
1000 Posts
Same remote start code? How often does that happen? I know that with keys you've got something way too common of a chance to unlock a door, maybe it's 1% or so, I don't recall the numbers. But how many remote unlock / start codes are there?
 

MT Madman

New Member
There is no physical key to unlock or start the engine other than the emergency key in the FOB. No remote start the car just the FOB and the start/stop push button. Been to Toyota 2 or 3 times with the problem and they want us to drop the vehicle, rent a car, and pay for troubleshooting time, I understand they are entitled to be compensated for their time especially now that it's out of warranty but it was the same story under warranty, plus it's difficult to repeat while there. I did read a post that someone in AZ had the same problem but I can't find it anymore, likes it's been wiped from the internet. I just hope it doesn't come to it starting in the (attached) garage at night while we're in bed.

It all comes to this, it's the wife's car and she doesn't trust it as much as she once did and she'll never want another Toyota.
 

toyotafan

Toyota Truck Club Founder
Staff member
1000 Posts
If you told them that it was happening under warranty then you have a very strong case for having it covered for repair if/when the cause is discovered. It's so unusual of an situation that I'm not even sure how to troubleshoot. If you could capture the next time this happens on video that would be good evidence and we could post it online for you to promote.
 

kennythewelder

Super Moderator
Staff member
100 Posts
There is no physical key to unlock or start the engine other than the emergency key in the FOB. No remote start the car just the FOB and the start/stop push button. Been to Toyota 2 or 3 times with the problem and they want us to drop the vehicle, rent a car, and pay for troubleshooting time, I understand they are entitled to be compensated for their time especially now that it's out of warranty but it was the same story under warranty, plus it's difficult to repeat while there. I did read a post that someone in AZ had the same problem but I can't find it anymore, likes it's been wiped from the internet. I just hope it doesn't come to it starting in the (attached) garage at night while we're in bed.

It all comes to this, it's the wife's car and she doesn't trust it as much as she once did and she'll never want another Toyota.
I totally understand what your saying about it being your wifies car, and not trusting it. I would feel the same way, and just like you, about it starting at night in the garage. The new vehicles have way to much tech in them IMO. Your best bet at this point may be to trade it in on something else, but no mater what you get, they are all loaded with tech unless you drive a classic. In 1990 I bought a Grand Am new. It went into the shop 18 times in 2 years. I gave up and traded it in on a mini van. Point is, you can get a lemon in any vehicle.
 

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