Q-DawgVFR

I just had a stupid moment. I switched the dead 4Runner battery for the one from my GM truck. Posts were offset in opposite direction compared to Toyota, and I set it in backwards. Realized my mistake just as the positive cable touched the negative post. The ground cable was just sitting on top of the positive post at the time. Unhooked it right away, but not before I noticed that the parking lamps were on. Tried hooking up correctly to asses damage. Vehicle is dead, and worse yet, there was a slightly burnt smell when I opened the driver's door.

Can anyone tell me where to start troubleshooting this? Where do I find the ECU and is there more than one fuse panel? I see the fuse box under the hood, but is there one inside the truck also? I'm fearing the worst; that I've fried the ECU or main wiring harness. I can't believe what a dumb, rookie mistake I've just made!!! Just goes to show what happens when your mind isn't on the task at hand...... .......I was thinking about the block heater I was about to change out! Hardly seems worth doing now. Any advice at all would be greatly appreciated, as this is probably going to get very ugly for me to fix. Oh yeah, my truck is a '96 4Runner LTD, and it has a command start 290i installed which could make troubleshooting even more difficult!

sts2usnss

There's another fuse box on the drivers side under the kick panel inside. Good luck....I think you are gonna need it.

04 Rocko Taco

I did the same thing 3 times in a row on a honda prelude once....we just blew the main 100A Fuse...I like that about that Honda...other than that...well, its just a honda.

Q-DawgVFR

Where do I find the ECU? Also, where are the fusible links located, if any?

I talked to Red Deer Toyota and explained situation to service advisor who took NO pity on me and informed me that their techs are paid to do paying jobs, NOT to talk to backyard mechanics who get themselves in trouble and need advice. I explained that theirs was the nearest Toyota dealership and that I needed to do SOME basic troubleshooting in case I had gotten off easily and only blown fusible links or fuses. I live over 40 miles from their dealership and can't just tow it in and have their people dissect the vehicle to find the problem, as this sort of thing has potential to write off a vehicle. I explained that if it wasn't an easy fix, they would likely be who I would turn to next, for reliable help. Apparently, they aren't interested enough in their customers to spend 2 minutes on the phone helping them out when they really need it. Not much Christmas spirit there!
Called Mayfield Toyota in Edmonton where I was treated much better. :bigclap: Talked to Chris, who informed me that this happens more than I might realize, and that he did not want to give me false hope.... But.... most people do get off lightly with only fuses and/or links fried. Told me to check through fuse box and test each circuit with test light to see if it is working. Record any bad circuit locations and keep moving on. Go through whole system that way to find out what is fried, then go onwards from there.
Took 2 minutes of his time to be nice; the same amount it took to be unhelpful at the other dealership. Makes me want to get any dealer servicing done in Edmonton, not Red Deer.

da_bigg_wigg

Hah, that sucks dude. My friend blew up his head unit in his Ford doing that, but he was too poor to get it fixed so he ended up rockin' out to silence for the longest time. Nothing else of his went though, lucky guy... I hope it's an easy fix, dude...

Q-DawgVFR

OK, just did some very preliminary checking out and found 3 blown fuses. One is the ECU/ign from the dash fuse panel, and the other two are 15A fuses located in the fuse box under the hood. Not sure what these are just yet. EDIT: they are the dome and ECU fuses. Question is this? Do I replace them and see what happens, or should I be more cautious and check some other things first? Not even sure if I have power to the fuse blocks at this point; my test light is too tiny to get into the fuse block properly. Thought I would go to store and buy some fuses and a better test light and see what responses I got from you guys.....

MTL_4runner

Same thing happened to another member on YT (Lee). His was jumped reverse poled so not entirely the same but it came down to being blown fuses preventing his from starting. Now I'm not saying you'll be able to just pop in some new fuses and get away scott free but the chances are high this was all the damage you did (fingers crossed for you). I'd just replace all the blown fuses and try to start the truck. If it doesn't start, double check the fuses again and then start additional troubleshooting as necessary.

Here's Lee's thread:
https://www.yotatech.com/forums/f2/please-help-fast-truck-isnt-starting-99279/

WATRD

If the main fusible link didn't go, then you probably have a bunch of blown fuses. Even if it did go, there are going to be a few.

First, find the BIG fusible link. Follow the battery positive toward the fuse box until you find it. Check it's condition first. The, once it is okay, start chasing down individual circuits and testing/fixing them as required.

This happens. It's not that uncommon and most times it's not major damage the vehicle. The elextrical system is usually smart enough to take care of it before major damage happens. Aftermarket stuff can be a different story unless the installer was religious about fusing and protecting.

Don't panic! Just chase it down one system at a time, starting with that main link.

Froggy93

fuses are the quickest and easiest to replace I would suggest replacing them and thern trying to run the truck. have seen this happen on a honda but not a 4runner. the honda was fine after main fuse was replaced. if a componet fried during the power surge, it is not going to hurt it to anymore anyways. turn the key to the on position first and see if any lights come on. if everything comes on normally, I would think you would be ok to try to start it. just watch out for that dredful blue smoke . good luck fingers crossed

Q-DawgVFR

OK replaced the blown fuses. I have a door chime and interior light that work. There is a 'door open' light on the dash (all encouraging progress) but when I try to start the truck, I get no signs of engine life. I can barely hear it, but it sounds like there is a relay functioning when I try to engage the starter. Tried the ignition switch at the 'run' position and noticed a red light on the radio, but none of the power windows would work. Not sure where to look next, but it seems obvious that there is still a big chunk of the electrical that is not in the picture yet. Am going to try to locate the main fusible link now to see its condition. Are there any fusible links other than what WATRD described?

Q-DawgVFR

Theres a lot of loom and heat shrink and tape all over the positive cable. Can I get better detail as to where EXACTLY the fusible link is, so i don't have to rip too much stuff apart? Oh, and some further signs; the headlights work, but no dash illumination. Also no power door locks.

Nam

Opps, sorry to hear that! Let's start with the electrical wiring diagrams first. From the battery, trace each branch and see where they go and what componets or fuses those go through and replace slowly. I think it's ok to replace blown fuses and test. If the components are bad, fuse will blow again...so what?

I don't think it's that bad. The ECU is located behind the glove compactment.

Good luck and keep us posted.

Nam

WATRD

The main link is going to be close to the fuse box. Possibly even under it or just inside it. I can't be more exact with your model/year, but I bet someone here can.

Q-DawgVFR

OK, I think I know where it is. There is a white wire which branches from the positive cable and connects to the fuse box. It kind of runs up through the side of it and is hard to the touch (really doesn't want to bend) and is covered in heat shrink tubing. It is retained by some sort of clip and cover to the corner of the fuse box, but I cant get the ^*$%ing clip removed. Must be idiot-proof! I'll try harder now that I think I am on the right track.

Q-DawgVFR

Oh, if anyone has any wiring diagrams for the '96 4Runner, then PLEASE link me to them or PM or e-mail me. I think I'm going to have to dig deeper, and it would really help me to know what each circuit contains and where to locate the various components. I've ordered a service manual from eBay over a week ago, but it hasn't arrive in the mail yet. It sure could have paid for itself by now if I had had one in my possession!

Q-DawgVFR

Behind the glove compartment just like my OBS GM truck. Was a pain to work with. Hopefully the Toyota is better!

rdharper

This is probably much more common that people would admit. It is relatively simple for Toyota to design protection since the reverse voltage is predictable.

The normal ground remains the common, so what you've done is put -12 where the +12 is expected. So protection with diodes and fuses is just a design problem. The diodes would prevent current flowing the wrong direction, and maybe steer the current to blow fusible link type fuses.

The fact that you observed the parking lights on says that the -12v did make it across those incadescent bulbs. They don't care what polarity is, just the net voltage.

Good luck and keep us aprised, as most people wouldn't have the courage to admit they made the mistake.... and we all might learn something.

runethechamp

Isn't the fusible link the main fuse on your positive cable, meaning that if you get light somewhere, that link is still ok? I would guess you have fuses in your engine compartment somewhere (I have in my 94 and I'm pretty sure the engine fuses are loated there), so I would check those as well.

WATRD

I think that link covers everything but the starter, so that should be true.

Nam

Alright, If I go home this weekend, I'll email you the wiring diagram since it's on my computer at home and I am 100miles away for work.

Yes, it's very easy to access the ECU.

Nam