Shorted battery - good Toyota indy?
 

So a week ago I managed to short my 2016 Tacoma's battery. I was disconnecting a powered 2AWG cable and accidentally grounded the socket on something nearby. Idiotic mistake, but it happened, and now I'm in the (expected) world of electrical problems.

The ground cable (from the negative terminal to the inner fender) went up in flames and its insulation disintegrated. I replaced that cable w/ a temporary 2AWG ground, but the truck wouldn't start. Had it towed to the dealer and they spent some ~4.5 hours working on it over the course of a few days.

The main fuses (140a and 120a for the alternator) did not burn up, the alternator seems fine, so does the battery. The dealer did some misc wire repair (not sure what this entailed). The truck started for them, then wouldn't start again the following morning. They then diagnosed no power at the EFI relay and either replaced it or did something else to fix it; the truck started every time since. I picked it up on Wednesday, ran a few errands, drove home and parked it. Tonight the truck again won't start. Computers/electrics turn on, but it won't crank. Check engine light is on, truck say check electrical system. Just like immediately after the incident.

So something else is clearly messed up. I'll be getting the truck towed to the dealer again tomorrow. I'm hoping they'll be able to figure out what's wrong, but I know how these electrical gremlin problems can go, and I'd like some backup options.

Are there any good indy mechanics that you'd trust for this kind of job? Fixing things properly is a must. I'm in New West, so someone nearby~ish would be preferred.

The only things that should have been damaged are the circuits involved. Assuming the engine was off that should be the battery, the ground wire for the battery, the cable between the positive terminal and where the socket was, and whatever the socket grounded to. There's no reason for anything else to have been affected.

Did the dealer replace the battery? If not, did they at least try a new battery pretty much right away? If they didn't they're just screwing you over (there's no way this should take 4.5hrs), and before you waste any more time with them go buy a battery and plop it in.

Thanks your reply.

The battery read 12.27 immediately prior to the first tow to the dealer, so I assumed it was still fine. I guess it's possible that it died in the last ~48 hours of sitting there.

Yes, the truck was off when this occurred. A good chunk of the ~4.5hrs was removing and reinstalling the PDC (main fuse/relay box). Toyota, in their infinite wisdom, made it so that the "serious" fuses (such as the 140a and 120a one I mentioned earlier) are bolted in from the bottom, and cannot be removed without lifting the entire PDC box. That's a well known pain in the ass (tons of info about it online).

Everything you've listed off is accurate. The battery is the only thing that comes to mind as a potential culprit. Fingers crossed it's that simple.

Another small caveat is that Toyota doesn't sell that ground wire separately, but rather only as part of the entire negative-terminal harness, running in at a cool $398+tax. And there's no inventory anywhere in North America, so it could be months before it comes in. I can easily find a wire of same guage and crimp it into the original location, but the dealers won't do this (probably for liability reasons). Honestly, I'd pay the ridiculous harness fee just in the off chance that someone else on it may be damaged (such as another thin ground) and would not show its ugly face until the most inconvenient moment. I have two big road trips coming up next year (1 month and another for 2 months) and would hate to run into electrical gremlins in the middle of nowhere. This harness has changed from the earlier years, so finding a used one is impossible.

I have seen ECUs being fried due to shorted wires

Did you manage to find out what the codes were for the next check engine light?

Just checked the battery - 12.56. Guess the easily solution is out. :(

I was worried about the ECU too, but then I wouldn't have been able to drive the truck after picking it up on Wednesday, right?

My Actron OBD II scanner didn't pick up any codes at all, but the dealer gave me a print out that included these on their initial scan:

http://i.imgur.com/DCBcijR.jpg

Also, I had a peek in the fuse box, at the relays the dealer's mechanic was talking about. The EFI relay has "horn" written on it w/ a sharpie, and the horn relay has "EFI 1" written on it. I guess they diagnosed a problem with the EFI relay and swapped it with the identical horn relay to see if that would help (having labeled the originals), and it did at the time.

Could there be some kind of voltage fluctuations (due to another burned off ground somewhere?) that would be frying the EFI relay? I guess I should check my horn to see whether it still works w/ the original EFI relay in place. Will do that tomorrow.

Don't just go off the voltage from the battery, you just dumped far more current than was intended out of it which can easily damage the internals and their ability to pass the current needed to properly start and run your truck. You need both voltage and current to do anything electrical, your battery might have 12V and enough current to run the basic electronics in the truck but if it can't put out enough current the engine won't crank and start. If you're worried about reliability I'd highly suggest replacing it unless it can be load tested, and a decent battery should only cost about as much as 1hr shop time at the dealer anyways.

Did Toyota tell you why they pulled the PDC? Did they test the fuses as blown before yanking it all apart or no?

For the damaged wiring, Toyota should be willing to repair the damaged section, at least Jeep did for my Grand Cherokee (under warranty).

They couldn't tell the state of the fuses/wiring without taking off the PDC. From the top things looked fine to my naked eye, but who knows...

Tow truck just picked it up. The service advisors I dealt with aren't in today, so I won't hear anything until Monday at the earliest. I'll ask them to do a battery load test.

So the truck came back from that dealership. They had replaced the EFI relay, but otherwise couldn't reproduce the problem.

Wouldn't start again on Wednesday night, had it towed to another dealership. They've replaced the negative ground harness at my request, and have been able to reproduce the cold-start problem. It's still there, and it sounds like they're not having any luck, either.

Last I heard they had traced it down to voltage fluctuations around the certification ECU and were going to debug that further, checking the input to that cert ECU. The voltage coming out from the cert ECU and going to the starter relay would be a low 8v when the truck is having the problem, and the specs call for at least 9v in that scenario. That's all I know, no updates since Friday.

Getting pretty desperate for ideas/fix at this point...

underscore is right. Low voltage on the start is easily attributed by a shitty battery. In fact it's the first thing. Does the vehicle crank at all when it doesn't start or is it just dead? Second thing to look into would be bad connections (or fried wiring), but it seems all the main arteries are new and intact.

They must have load tested the battery by now, no?




I forgot to strap my battery down once, and it decided to launch out of its holder during some spirited driving. Besides blowing out my exhaust (due to the massive backfire), a small fire at the battery terminal (Which I put out with my hand... smart) and a battery welded valve cover my car was great (After replacing the battery terminal with a bunch of 10awg terminal I had in the hatch). Gotta love old cars. I have a feeling if I made the mistake now I'd have a bit more of a problem with the Megasquirt.

They did do the battery load test and it came back very healthy. Is it possible that something is damaged in the battery that the load test does not "pick up?"

I actually just spoke with the tech. Says the truck started just fine all day today, so they haven't been able to debug it further. They will try again first thing tomorrow morning - if it starts, I'll be picking it up and waiting for the problem to reoccur. I can swing by Endmonds Batteries on the way home and see if they can run their own battery health test on it.

I should have asked if the voltage drop was during cranking, or the starter relay has a lack of voltage even prior to cranking.

If the battery load tested ok, i'd say it's time to keep looking. Curious if the vehicle is left outside tonight or not. Will take some more juice to turn that over at -1, then 10-15 degrees that the shop is held at.

I think/hope they're leaving it outside.

I forgot to mention to this earlier - the vehicle does not crank at all when the issue is happening. Starter relay does not get power, and the voltage drops happens before the starter relay. It was definitely happening on the output of the certification ECU (to the starter relay). Further diagnosis hasn't happened as the truck has been starting.

If they boost the truck by giving power to the starter, it does power on, but subsequently dies after driving a few metres and changing from drive to reverse.

Just confirmed that the truck is outside tonight.

Well hopefully they can figure it out soon. I'm curious if the ECU steps the voltage down always, or something else is going on there as well.

Just to be clear, I'm talking about the "certification" ECU, not the main ECU. This fella is responsible for ensuring the vehicle is in park, brake is depressed, etc. - basically all factors that have to be in play before a vehicle is allowed to start.

Anyways, I'm almost certain it is NOT supposed to drop down the voltage, but rather pass it through as-is. Tech's next planned diagnostic steps (whenever this can be reproduced) is to measure the voltage coming in to the certification ECU, and if that's still low, the voltage on either side of the "junction connector" (not sure what this is) that is located behind the glove box area.

So they checked the voltage coming out, saw it was low, but didn't bother to then check the voltage coming in?

At the time the tech wasn't 100% sure where the voltage was coming in, and by the time he figured it out, the truck decided to start firing up.

Just heard from the tech. Truck was outside all night, fired right up this morning. It's -1C in Vancouver right now, so there's no way the truck is warmer than that.

The first two times it wouldn't start in my underground it was around 12-18C.
The last time it wouldn't start (last week) was outside, around 0C.

There's no consistency to this damn thing.

FML.

Did you do any modifications to the truck?

Some guy at tacoworld had electronic problems after installing morimoto LED +driver. I had trouble starting when I tapped the ignition circuit for proximity sensors, truck would struggle to start regardless if the system was on or off. Tapped the window motor circuit and it was okay afterwards.

Tons of mods, but none that would interfere with the starting process. None of my electrical stuff is hooked up at the moment (while dealing with this problem).

Picked the truck up this morning (was starting fine), drove it 30 minutes to Burnaby, and it wouldn't start again. Tech suggested trying to start it in neutral, and lo-and-behold, it fired right up. Immediately after it started in park, too. Tech thinks it may be the neutral safety switch at fault here.

Being able to start from neutral is a huge relief (provided that continues to be the case), as I can't express how tired I am of getting stranded/stuck with a non-cranking truck. Will continue to use the truck and see how things go - if this scenario reproduces consistently a few more times, it should be easy enough (although not cheap) to replace the neutral safety switch.

And yes, I've seen the morimoto-problem thread. One strange thing I had encountered with this Truck's electrical (early this year) was when I was hardwiring my radar detector and dash camera, I was looking for a switched 12V. Found one, tapped it, and then boom, it would only show 5V instead of 12V when the truck was running. Then it would randomly show 12V again, then back to 5V. Turns out the new Tacoma does this kind of "pulsing" across many different circuits - first you get one voltage, then another at a different time. This was a head scratcher. But anyways, that's not related to the starting problem.

It sounds like your truck have a few systems that use PWM. PWM system is controlled by a processor which modulate the electrical system by turning the electrical source on and off rapidly (more for higher, less frequent for less). Things like AC, variable lighting that uses LED would use PWM. Each system eg AC would have their own processor, the problem arises is those processors are really sensitive to surges. They might check out okay, but they might loose their ability to swich on and off well.

Is your truck leased? it might be a good idea to just trade it in when the new model comes and let someone else figure it out.

not trying to hijack this thread, but does anyone have a reliable toyota mech? pls pm! tyvm