Most likely your 12V battery is half-dead. Try jumping the 12V battery from your other car. There is a dedicated connection point under the hood to connect the + jumper cable next to the main fuse box. Connect the - cable directly to the engine block.

 

Hi Katekebo,

I tried jumping it with two different cars, and even let the second car sit running connected the the highlander for 5-8ish minutes before attempting to start the Highlander.
Not a fan of that Pos jump point, but I made sure the correct 'hot' tooth of the pos jump lead was on the metal side of the pos connection in the fuse box.

I guess I should try and directly measure the voltage of the 12v. Is that very easy on these? Didn't see the battery, guessing its in the trunk or something. Or can I just measure from the frame to that fuse box Pos jump point?

 

Welcome to the forum @yotas4me !

I guess I should try and directly measure the voltage of the 12v. Is that very easy on these? Didn't see the battery, guessing its in the trunk or something. Or can I just measure from the frame to that fuse box Pos jump point?

The 12 Volt battery is located in the rear passenger side corner of the vehicle. Open the liftgate. On your lower right there is a panel with two latches that is easily removed to access the battery.

A Toyota Hybrid requires little current from the 12V battery to initialize the vehicle but does expect a solid 12 volts.

The only way the vehicle can recharge the 12V battery is by drawing from the traction battery. The traction battery is what actually "turns over" the gas engine and if allowed to excessively discharge it will be unable to do so. Now you are stranded until the vehicle can be brought in to a dealer to replenish the roughly 300V traction battery.

Hopefully this is not the case.

Probably best to connect the 12V battery to a battery maintainer if the vehicle is going to be unused for more than a few weeks.

FYI - There is a dedicated forum for the Highlander Hybrid located here:

Toyota Nation - Highlander Hybrid Forum

You may receive more responses to Hybrid specific questions there.

 

The vehicle is pretty good at protecting the integrity of the traction battery and would not be the first thing to suspect.
Focus on the 12V battery. There have been a few reports of really strange vehicle behavior with a defective 12V battery that wasn't obviously bad.

 

Make sure you are using a good quality jumper cable with copper conductors.

 

If that 12V battery sat connected for three months, it's probably shot and no amount of jumping/charging will help it. Once you drain the battery past a certain point, it's never going to hold a good charge again.

I did that once to a battery in a Tacoma. That only took three weeks of sitting, but a conventional non-hybrid setup is quite different. I thought I was able to charge it, only to have it be completely dead again the next day.

 

Hi toto, you might be right.

I pulled the battery (reading ~8V) and charged it over night. it seemed to hold just fine for a day at ~12.5V. Put it in and no change. Other than the locks and liftgate now work, still get the same response from teh dispay, "Press brake and Touch Key to Power Button"

 

Not an easy task but change out the battery with the 4Runner. Then put a Battery Tender on it. I plug in my car every night to keep the battery up at all times and last as long as possible.

 

Thats not a bad idea. Extra work, but as I said above the factory battery held all day at 12.5 V off the charger, so it seems fine to me. I imagine there is more going on than just measuring voltage can tell you.
I didn't have my meter on me when I installed the freshly charged one but I'm curious now if its down to 10V or something. Its just weird I get no attempt to turn over or any response from electronics.

 

What was the status of the traction battery before the three month storage, i.e. how many segments were lighted in the battery icon display? The traction battery, like all rechargable batteries, is subject to an internal power drain with time. Good idea if not using the hybrid for more than a few weeks to start the vehicle until the ICE runs for at least 15 minutes to recharge the traction battery.......and enter storage with a close to full, almost all lighted segments, of the traction battery.

In normal use the system never lets the charge go below two segments without an electric motor/regen recharge to prevent deep battery drainage causing the system to go into protection mode. In protection mode the HV relays on the traction battery assembly will not close isolating the discharged battery from the system, i.e. so no EV mode or cranking of the ICE. If the vehicle entered storage with only two or three lighted segments there exists a very good possibility it is discharged past the protection point and must go to a dealer to recharge the traction battery.

One could try disconnecting the 12v trunk battery from the system for about 1/2 hr to erase stored codes then reconnect with a charged battery and retry......probably lots of codes thrown and may be able to bypass lockout protection and get the relays to close, but the safety of this approach regarding damage to a severly discharged battery is not known.

 

Thanks Thomcat, found cold cranking amps of 12V to be about 10 so replaced the battery. Still no change, AAA came out and tried to code a new key but was unsuccessful... They didn't have a good explanation as to why. Going to tow it to a dealership. Hopefully the fob is just dead somehow, because I would think we should at least get some helpful messages if it couldn't start.
Pretty frustrating.

 

Any update or what was worked on that fixed the issue?