Reversed jumper cables?

DESERTDOLPHIN

MEMBER
2007 TOYOTA SIENNA
V6
2WD
AUTOMATIC
100,000 MILES

I have an older van listed above that was discovered to have a bad battery (old battery, wouldn't hold a charge or start the car). I had also noticed that it had maintenance required and low tire pressure lights that stayed on, as well as a parking brake issue. The car is not driven that frequently. Yesterday we to jump started it, and it started up without problem, drove it briefly, and planned on taking it to the mechanic this morning. This morning, the battery was drained, so we hooked up the cables again, but got in a hurry and reversed the cables on the drained battery. Neither the car nor the truck we were starting it from had been turned on yet, but after about 5 seconds, my friend noticed that some white smoke was coming from the dead battery, and a warning alarm started beeping. I immediately realized what I had done and yelled at her to take the cables off, which she did.
We put the cables on the proper way, and the car did start up without a problem, but there are now (ABS, air bag, and an additional one I haven't looked up yet). My friend noticed that the car windows would not go up or down, and the car won't go into gear from park, which I am hoping is a fail safe switch of some sort.
I am hoping that the fact that it was hooked up very briefly and that the engines had not been started yet, and also that the dead car did start right up afterwards are all good signs, and I am planning on having the car towed to the repair shop tomorrow.
what are the most likely things that would cause the problems noted above-blown fuses are my first thought, but I have no idea why the car would not go into gear.
Thanks so much for any ideas or advice you might have.

10 Replies

CARADIODOC

MECHANIC
33,729 POSTS

Yes, there's going to be multiple blown fuses. Due to the age of the vehicle, there's going to be a lawyer-approved shifter interlock that requires the brake pedal to be pressed to shift out of "park". That solenoid is energized by the same circuit that powers the brake lights. Chances are one of the blown fuses is for the Body Computer or lighting computer. If I'm right, your brake lights won't be working.

You might want to check out this article:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

All computers have at least two 12-volt inputs that are fused, and inside all computers there's a diode between ground and each 12-volt supply specifically for when a battery cable or jumper cable gets reversed. A diode is a one-way valve for electrical current flow. They're placed in the circuit backward, so under normal conditions, it's like they aren't even there. It's when the polarity is reversed that the diodes become "forward-biased" and act like a piece of wire. That dead short they create causes the fuse to blow, thereby saving the computer. Computer circuitry is very intolerant of reverse polarity; hence, they added the diodes. In almost all cases, you correct the reversed polarity, replace the blown fuses, and you're back in business.

These three drawings show the locations of the multiple fuse boxes. They also point out "fuse links". Those could be rather large fuses, both electrically and physically, or they might be "fuse link wires". Fuse link wires are used in circuits with a very high start-up current, like for motors, where a regular fuse would blow too easily. Fuse link wires are slow-blow fuses that need some time to burn open. I wouldn't bother with testing those for now as they are likely to be okay. They also usually protect a number of circuits, so only suspect a fuse link wire if a lot of circuits are dead. You tug gently on them to test them. If they're good, they'll act like a wire. If one is burned open, it will act like a rubber band.

Let me know what you find.

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Monday, November 28th, 2022 AT 7:17 PM

DESERTDOLPHIN

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Thank you so much for such a helpful reply. I checked the brake lights and, just as you suggested, they did not work. Right now, the things I've noticed not working are brake lights, door lock and window switches, and the check engine/ABS, and air bag lights are on.
I forgot to mention in my first email that it is a 2003 Sienna.
I'll let you know what is found after I get it checked out.

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Tuesday, November 29th, 2022 AT 1:19 PM

CARADIODOC

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Point of interest. Just about all computers have a minimum of two 12-volt power feeds. Engine Computers commonly have four. ABS and Air Bag Computers in particular will always have two 12-volt power wires so one of them can run the circuitry to run the dash warning light when the other one has a blown fuse. That's done for safety. If there was only one fused 12-volt circuit, and that fuse blew, you'd never see a warning light or know that system was inoperative.

My cousin has a 2003 Sienna. I was surprised to see so many fuse box locations for a 2007 model. One under the hood and one inside is typical. Let me know if you're trying to solve this on your own. I'll look for the fuse box locations for a 2003 if you need them.

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Tuesday, November 29th, 2022 AT 7:29 PM

DESERTDOLPHIN

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Hi, thanks again so much. We just decided to have the vehicle towed as it had other things, we had been taking it in for anyway. They said they tested the fuses and found the main fuse block needed replacing, as well as the battery of course.
Interestingly, when we had the car towed, we had not been able to get the car in to gear (fuse blown to the solenoid running the brake pedal safety switch?). When the tow guys arrived, they got it into gear by pulling up a cover over a(override?) Switch on or near the shifter handle. They were then able to put the car in gear and were actually able to drive it out. I thought that was interesting as I didn't know anything about that.
I'll let you know more when I hear the final diagnosis. Does what the shop has found so far sound reasonable?

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Thursday, December 1st, 2022 AT 3:16 PM

CARADIODOC

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The hidden shifter over-ride lever or switch is common but usually hard to get to.

It should not be necessary to replace the entire fuse box. One of the purposes of the fuses is in case the battery or jumper cables are reversed. Unless they can show you where something burned up or got damaged, I'd question that.