Won't start, lights work, locks don't

I believe fuses are to protect conductors, when it comes to the semi-conductors in electronics, it's a crapshoot, and the odds aren't very good.

 

My background is GM having read these symptoms, and no start complaints, I would be looking for a burn" Fusiable link" in the main body harness. but that's just me.
Are there Fusible links in this Toyota ? I would really like to know what it took to repair this issue.

 

I know the older Lexus and Camry models have a fusible link. I would think that would've been superseded by a main fuse.

 

They were reversed. Was bullshitting and not paying attention. New battery, no blown fuses that I can see. Haven't checked the main fuse, yet.

 

Like I stated, it's not impossible but probability would favor the fuse blowing to protect the ecu.

Also you need to consider the amount of cranking amps those "AAA" tow trucks can deliver. Far beyond that of a normal car battery.

 

I can't confirm nor deny that we (I work for AAA as a Tow truck operator) haven't fried the f*ck out of a few (maybe more, maybe less) ECU's. If you smell electrical smoke in the cabin, good chance the cables were put on backwards, and more than a fuse was blown.

 

The main fuse between the generator and battery is 120 A with the standard generator, and 140 A with the high output generator option. With an 800 A load it would take 750 to 800 ms (just a bit less than 1 second) for either of these to blow--for electronic devices 750 ms is an eternity, almost without exaggeration it may as well be 750 years .

Here is the charging system wiring diagram:



There is good news (sort of) however as the ECU is protected by a 20 A fuse which would blow much faster, 10 ms or so, with that same 800 A load--still a long time in electronic terms but maybe, maybe, enough for any internal reverse voltage protection in the electronics to do their job¹.

Replacing the 120/140 A fuse requires that the inner fuse box assembly be removed from the outer assembly so that the fuse's mounting bolts can be removed/reinstalled. There are a number of write-ups on the web and even some YouTube DIY videos of varying usefulness...


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¹ - I do not know whether the various electronic modules have any internal RV protection--they may not as it is something that should never be needed.

 

The amount of cranking amps means nothing. The current draw is determined by the load not the source.

You need to attend a good electronics class. There is a world of difference between an electronics fuse a standard fuse and a slow blow fuse.

Response Characteristic:
The speed at which fuse blows, depend on the amount of current flowing through its wire. The higher the current flowing through the wire, faster will be the response time.
Response characteristic shows the response time for over current event. Fuses which respond rapidly to the over current situation is called ultra fast fuses or Fast fuses. They are used in Many semiconductor devices because semiconductor devices damaged by over current very rapidly.
There is another fuse which Is called Slow burn fuse, switch fuses do not respond rapidly to the over current event, but blow after several seconds of over current occurrence. Such fuses found their application in motor control electronics systems because motor takes a lot more current at starting than running.

Vehicles do not use ultra fast fuses.

 

I wonder what the load imposed by a reverse connected battery would be? Reverse current flow through the generator diodes would likely be a big (maybe the biggest) chunk of it.

A bit of research turned up ISO spec (16750-2, Road vehicles—Environmental conditions and testing for electrical and electronic equipment—Part 2: Electrical loads) which states in part that for 12 V systems, modules must survive –14 V on the VBAT input for 60 seconds without damage. However I do not believe this to be a binding standard...

 

Here is a time-current relationship chart for LIttleFuse's ATO bladed fuses--it can be kind of scary.

If you follow the curve for a 20 A fuse you will find that when subjected to a 30 A load a 20 A fuse takes 4 seconds to blow...

 

The alternator fuse was blown (along with a few others). I have everything back but the stereo. Still going to take it in since the check engine light is on, but at least I don't have to have it towed. Thanks for all the suggestions. Also, changing the alternator fuse is a gigantic pain in the ass. Next time, I'll just pay attention to what I'm doing.

 

Glad you got it running.

 

Cool, the generator fuse looked like a PITA to get at...

 

Thanks for sharing the repair, Good luck going forward.

 

Well here is my two cents. If nothing like the starter, radio, even your OBD2 connector are not working then most likely it is your alternator main fuse. This is your primary 120A fuse. How do I know? I just spent over two hours getting to the one that the AAA guy blow when he replaced my wife's battery on her 2008 Camry. After he installed the battery, nothing worked, only a few dash light and interior light. I asked her if she heard anything strange during the install and said a loud popping sound. Well that clearly indicated that he somehow touched the negative terminal connector to the positive causing the fuse to blow. Getting to this fuse is one of the hardest things I have ever experienced. It entails dissembling the main fuse box and I mean the belly of the beast, equivalent to brain surgery. Not recommended for the faint of heart or inexperienced mechanics. I saved a lot of money doing it myself but there were moments when I was about to give up and just tow the car to an electrical shop, but I was determined. I don't know how our Tacoma's are wired, but I would assume that all Toyota's are similar.

 

The idiot probably tried to install a group size 24 battery, most Toyotas use a 24F or 27F:



This is a group size 24, see the difference:

 

that's a scary looking fuse!

Congrats!

 

Thanks for all the follow up, I learned a lot ( especially what happens when you misstep when jump starting)

 

I believe you are right as the battery installed is a 24F reverse pole and he probably did not know the difference.