Weird electrical issue on 2015 Trail

[wfo9]

It turns out the charging unit and/ or the plug part that goes into the outlet is a 9V device. The outlet is 12v. Which to me wouldn't seem like it would cause a problem. If it was over 12v then yeah sure that would be an issue. Any thoughts?

Those cigarette lighter style receptacles are a de feacto standard 12v DC accessory connector. Even though the device itself may require 9v, it would be the job of the internal power supply of the device or the cord and connector to deal with the conversion (could just be a simple resistor...). In other words, all those style of connectors are expected to see 12V in the receptacle, so that is not the issue.

 

[blacktrdpro]

This sounds similar to issues I've seen several times. I suspect you have an intermittent loss of ground. Without seeing the manual, I'd guess you have a self-tapping ground screw located on the lower interior a-pillar that shut off the torque wrench before it fully seated. It would be helpful to list all off the affected systems, then have a technician check the grounding and power circuit for intermittent connections.

 

[Ezekiel2222]

What appeared to have caused my problem was when the walkie talkie charger unit was plugged directly into the cigarette outlet. I use the actual wall type 400w outlet for the same unit in the cargo area now. No issues sinc.
Also they took a BCM right off another trail that had just got to the dealership. I may have pushed for that but by day 30 something I was irritated.

Very interesting. I wonder if testes1010 had the exact same walkie talkie charger unit as you, and if he plugged it into the same outlet? Who made the unit if you don't mind my asking? A reputable big-name brand, or some cheap Chinese knockoff? Any reason to suspect that the unit might have somehow overloaded the outlet?

Of course, I'm not sure what any of that would mean for me, other than the fact that both of us added something to the system that increased the power draw, and both resulted in the same problem.

blacktrdpro: I originally suspected something similar, as the problem would come and go at random times. Unfortunately now it's in a perpetual state of "problem". I can't remember the last time my dome lights came on! Is it possible that an intermittent loss of ground could have eventually fried something like the BCM?

 

[wfo9]

Is it possible that an intermittent loss of ground could have eventually fried something like the BCM?

I think so. My theory (although it is just a theory with very little evidence to back it up). is that there is some underlying flaw that certain loads expose. An intermittent ground could be a possible culprit.

In your case it sounds like the BCM may be fried, but it is mind blowing to me that Toyota cannot determine this within a few minutes of testing.

 

[tacoma22]

Very interesting. I wonder if testes1010 had the exact same walkie talkie charger unit as you, and if he plugged it into the same outlet? Who made the unit if you don't mind my asking? A reputable big-name brand, or some cheap Chinese knockoff? Any reason to suspect that the unit might have somehow overloaded the outlet?

Of course, I'm not sure what any of that would mean for me, other than the fact that both of us added something to the system that increased the power draw, and both resulted in the same problem.

blacktrdpro: I originally suspected something similar, as the problem would come and go at random times. Unfortunately now it's in a perpetual state of "problem". I can't remember the last time my dome lights came on! Is it possible that an intermittent loss of ground could have eventually fried something like the BCM?

I believe the walkie talkies are midland's brand. I'll double check when I go outside. It did it no matter which outlet I used.

 

[blacktrdpro]

I should note, my experience with these matters was about twenty years ago. At the time, I resolved GM lemon law cases, mostly electrical. I doubt an intermittent loss of ground would fry a control module, however this has all the signs of a ground loss. Also, it could be a terminal that is not fully seated in a connector. Possibly where the IP connects to the chassis harness. It is helpful to identify all the affected circuits, then look for the common link. The suggestion of a loose battery terminal is good, but this usually affects powertrain components. As for the heated seats, I doubt it is related, but it may be worth checking to see where they tapped the power feed. They possibly could have caused an intermittent power loss or cut a wire with a tap connector that drives a spade through the wire.

Edit: BTW If the dome light has stopped working, that's a good thing. Now you can duplicate the problem. Let me make an odd suggestion. Open both front doors, confirm the dome light is off, then slap the right kick panel, if that doesn't turn on the light, slap the left kick panel. If that doesn't work, get a second person to watch the light as you open then close the hood.

 

[testes1010]

I believe the walkie talkies are midland's brand. I'll double check when I go outside. It did it no matter which outlet I used.

Mine are Midland's as well. Great radios for the price.

 

[Ezekiel2222]

So I finally got my vehicle back from the dealership after having them replace the BCM with a stock one. Turns out when they installed it and tried to start it they were still getting the same errors and such, and after a few extra hours of troubleshooting they discovered that the "short pin fuse" was blown. My service writer told me this fuse is located under the hood, and he swears it was not blown when I first brought my vehicle in two months ago. They replaced the fuse and were able to reset the system and everything appears to be working now. Of course, they did NOT re-attach the heated seats, so now I have to decide if / when I want to try that again. Naturally I should wait at least a few weeks to make sure the problem doesn't come back on it's own, but if I wait too long winter will be over...

I'm curious which problem came first, the BCM or the fuse. In other words, did the failing BCM cause the fuse to blow, or perhaps did a faulty fuse cause the BCM to die, and in either case, did my heated seats have anything to do with it?

 

[96r50]

That's interesting. The short pin is installed during the Pre Delivery Service (PDS). Check out the attached file for more info, and have a look at the red "Note" box on page 2 where it says this:

• Removing the Short Pin cuts off power sources relating to the DOME, RADIO No. 1, and ECU-B fuses.
• The Short Pin does not function as a fuse, so install it only in the position shown.

It's not actually a fuse from what I can tell, just a jumper that disconnects certain circuits to minimize battery drain during transport and storage before sale. I wonder how yours "blew"?

I'd leave the heated seats disconnected for at least a month or two and see if the problem comes back. At least that way if it does you know it's not the seats. If it doesn't, well.... :wow:


Edit: here's a bad photo of the Short Pin (the yellow one in the top of the photo). Note the little wings on each side that prevent it from being installed in a regular fuse slot.

 

[BlackWorksInc]

If it is a true short pin (odd looking micro fuse) then it is nothing more than a metal bridge, it is not designed to blow at a certain amperage. I forget if the 5th Gens use that or a 30amp DCC fuse.

Needless to say, I'd be curious what the short pin looks like after it failed.

 

[96r50]

According to this diagram from the EWD the Short Pin supplies 12V to the DOME and ECU-B fuses. The owner's manual list those fuses as supplying power to the interior and vanity lights (DOME fuse) and the multiplex communication system, meter and gauge (ECU-B fuse). I'm guessing the BCM is included in the multiplex communication system but maybe [MENTION=66389]BlackWorksInc[/MENTION] can clarify? Given the symptoms listed in your first post I would think that this may have been the problem. I would verify that the Short Pin has good connections (check that the metal contacts it clips into are solidly held in place in the fuse box and that the connections to and from the Short Pin are solid).

If the problem does happen again you should be able to use a multimeter to narrow it down by checking for 12V on pin 1 of the Short Pin (end closest to the firewall). Then check pin 2 of the Short Pin (end closest to the grille) for 12V. Then check pin 1 on both the Dome and ECU-B fuses to see if they have 12V. Somewhere between the last good 12V reading and the 0V reading would be the issue.

 

[Ezekiel2222]

• Removing the Short Pin cuts off power sources relating to the DOME, RADIO No. 1, and ECU-B fuses.

Well damn, based on that it sounds like a defective short pin could have been causing all my problems! Maybe it was loose or something. My service writer swears it was one of the first things they checked when I brought it in two months ago, and apparently it was fine then. Maybe it was in the process of failing when I was having the intermittent problems, and then finally failed when my problems became permanent? I'm still curious what the short pin, the BCM, and my heated seats have to do with one another...

EDIT: 96r50 beat me to the post! Definitely makes me wonder if the BCM was just fine...

 

[Ezekiel2222]

I finally got a chance to go take a look in the fuse box. Sure enough, the short pin is a specially shaped "fuse" with no number stamped on it.

Is it safe for me to remove the short pin and then start up the vehicle? I want to see if I can re-create the problematic symptoms I had before, in an easily reversible way. If it turns out the short pin is the cause and solution to everything, it will make me wonder why they were messing with the BCM at all.

 

[BlackWorksInc]

The vehicle will run with the short pin removed I have only seen one go bad before; again its just basically a plastic encased metal bar for all intents and purposes, so it wouldn't surprise me if it got overlooked.

 

[K9trainer]

Sounds like Toyota was to busy blaming others to get down to the real problem. If they would have tried a replacement BCM long time ago to could have been solved long ago.

 

[Blitzkrieg]

Sounds like Toyota was to busy blaming others to get down to the real problem. If they would have tried a replacement BCM long time ago to could have been solved long ago.

Oh come on now.

Do you not think if the dealer felt that replacing the BCM would have resolved the issue and gotten this guy out of their hair a long time ago they wouldn't have done that from the get-go?

I am not saying all dealerships are great, but collectively at any dealership you probably have at least one or two techs who are savvy and have been around the block a time or two.

You can criticize a person or people but at least be fair about it.

 

[K9trainer]

Isn't that what they determined it to be?
From the post about the meeting with the rep and manager from the get go they were blaming it on the seats

 

[Ezekiel2222]

So I played around with the fuses today and made some interesting, if not obvious, discoveries:

The short pin was seated quite tightly (I needed needle nose pliers to grab it and pull it out.) It is most definitely just a piece of metal, and not a true fuse. Upon starting the vehicle with the short pin removed, ALL the symptoms of my earlier problems were back; inop door locks, lights, clock, blinking indicators on the dash, everything. Replacing the short pin and restarting the vehicle restored 100% functionality.

Removing just the ECU-B fuse and restarting the vehicle again gave me all the symptoms of the earlier problem, with the EXCEPTION of the dome lights, which still worked fine. Replacing this fuse again restored all functionality. As expected, when I then removed just the DOME fuse, the lights stopped working, but there were no other symptoms.

I called back my service writer to have him explain what exactly was wrong with the short pin. Turns out it wasn't "blown", but rather they found that it was not fully seated. He swears that they checked it on one of my earlier visits, and it was fine at that time, but one of his techs must have not replaced it properly. He also still swears that the BCM needed to be replaced...

My problem is this: If the BCM were truly dead/dying, the dome lights should have still worked fine, because as I proved above, pulling the ECU-B fuse and completely disabling the BCM had no effect on the lights at all.

The only possible explanation is perhaps the first few times the symptoms happened the lights were still working and I just didn't notice, and it was only after I brought it into the dealership the first time (and they messed up the short pin) that I started noticing the lights. It's honestly been so long that I can't really remember. However my service writer doesn't even support this hypothesis, because he said they checked the short pin on one of my later visits, when the FST was down from Denver.

What does any of this mean for me now? Should I go ahead and re-hookup my heated seats? Who knows!

 

[mo_mo]

I've been following this thread for a while and I'm glad you're still chasing this.

I wonder what the tech did to 'check' the short pin. Placing a simple electric test / voltmeter across the short pin would only tell a tech that the short pin wasn't shorted, but it wouldn't tell the tech that it wasn't seated. Depends upon where the tech places the probes and hindsight is unfortunately 20/20 and fuzzy.

If you do plug in the seats again, then let us know if you have any problems (coming from someone who will not be installing heated seats since I had the A/C blasting today).

 

[96r50]

So I played around with the fuses today and made some interesting, if not obvious, discoveries:

The short pin was seated quite tightly (I needed needle nose pliers to grab it and pull it out.) It is most definitely just a piece of metal, and not a true fuse. Upon starting the vehicle with the short pin removed, ALL the symptoms of my earlier problems were back; inop door locks, lights, clock, blinking indicators on the dash, everything. Replacing the short pin and restarting the vehicle restored 100% functionality.

Removing just the ECU-B fuse and restarting the vehicle again gave me all the symptoms of the earlier problem, with the EXCEPTION of the dome lights, which still worked fine. Replacing this fuse again restored all functionality. As expected, when I then removed just the DOME fuse, the lights stopped working, but there were no other symptoms.

I called back my service writer to have him explain what exactly was wrong with the short pin. Turns out it wasn't "blown", but rather they found that it was not fully seated. He swears that they checked it on one of my earlier visits, and it was fine at that time, but one of his techs must have not replaced it properly. He also still swears that the BCM needed to be replaced...

My problem is this: If the BCM were truly dead/dying, the dome lights should have still worked fine, because as I proved above, pulling the ECU-B fuse and completely disabling the BCM had no effect on the lights at all.

The only possible explanation is perhaps the first few times the symptoms happened the lights were still working and I just didn't notice, and it was only after I brought it into the dealership the first time (and they messed up the short pin) that I started noticing the lights. It's honestly been so long that I can't really remember. However my service writer doesn't even support this hypothesis, because he said they checked the short pin on one of my later visits, when the FST was down from Denver.

What does any of this mean for me now? Should I go ahead and re-hookup my heated seats? Who knows!

Thank you for following up and for keeping us in the loop. It seems to me that the source of your problem was the short pin not being fully seated and therefore intermittently cutting out and causing the issues you noted. I'd guess that the BCM was still completely fine since the ECU-B fuse was intact (meaning it didn't draw any excessively high currents) and given that the vehicle is designed to be operable without the short pin in place.

If it were my vehicle I'd be comfortable hooking up the heated seats again at this point as it seems like they were totally unrelated to the problem as you originally suspected.