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‘07 highlander hybrid having weird intermittent electrical issues

Hey everyone- first post here.

Got an ‘07 highlander hybrid that we’ve had for the past 13 years. It only has 80,000 miles on it as we live in the city and barely ever drive it.

A few months ago, we were driving and the car said “check hybrid system” on the dash. It still drove so we didn’t think much of it and planned to take it to the dealer when we had time. Next time we started it, the car wouldn’t drive because the error code locked it out is what I am guessing. We had it towed to the dealer, where they told us our issue was “water entering the hybrid battery,” charged us $400 in “diagnostics” during which apparently all they did was clean out the water channels on the roof. They didn’t even look at the hybrid battery or anything, but after a few days of it sitting at the dealer the issue went away. Fast forward to a few weeks, the light came back on. This time, we drove straight to the dealer to avoid another tow. This time, they got a code out of it that they said led them to an inverter issue but again the code went away. They refused to look at it further after that.

We took the car back, and it was fine until yesterday when we tried to start it. Now it does absolutely zilch when we try to start it. No lights, nothing even when we jump start it. We will have it towed today to a different dealer to see what they think, but I figured I’d get some peoples’ opinions here about this.

Thanks in advance!

How old is the 12v battery?

Not that old. Also, wouldn’t it start with a jump or at least show some lights on the dash with a jump even if the 12V battery was dead?

My MKZ hybrid wouldn’t start with a jump with a dead 12V battery, similar system to yours. I’d have the 12V battery checked, just to make sure it’s good. All kinds of odd problems can crop up if it’s bad, or just low on charge.

Yeah it did cross my mind. Did yours show any dash lights? I can’t even get this thing into neutral.

Mine wouldn’t shift, either. I don’t remember about the lights, it’s been a few years.

Thanks for the advice, having it towed to dealer later today so I’ll ask about it. Another thing I just realized is that it seems to be weather-related. It only has issues after heavy rains…

It sounds like you need to go to another dealer.

WTF… Trouble Codes do not just “go away”, unless they’re erased they stay forever. IIRC Toyota had a recall & long extended warranty on the Highlander inverters, which might still be in force.

You must go to a different dealer, or mechanic familiar with these Hybrids;
current guys sound like they like to make money ($400 in diagnostic work with NO diagnosis) but are afraid to do any work.

BTW, these cars are usually very reliable,a friend bought an '06 with 150k, ran it out to 270k, in 2017 traded for another '06 Highlander Hybrid with 95k miles. Only ever minor problems with both cars

Thanks for the advice. Yes, that is exactly what I thought about that dealer, we won’t be going back there. No independent mechanics around here that work on hybrids unfortunately. However, I did get the car to start with a new 12V battery, so it’s working for now. I don’t believe the inverter is still under warranty for this car though. If it needs an inverter we’re just gonna get a new car, not worth spending more than the car is worth on it…