ENGINE BAY MAIN FUSE BOX MALFUNCTION / LOOSE CONNECTION? (1 Viewer)

[pmrosendo]

I've looked through many threads on the forum trying to find something similar, without success, so here it goes (sorry for such a testament):

After a very hard 10.000kms+ on the 2024 Sahara Desert Challenge (11th) edition, with Morocco, Mauritania and Senegal hard tracks and trails, I had a very hard time to figure out and to solve a very bad issue on my '15 VDJ200...

It all began after the headlight washer started to work by itself, continuously, even with the car locked.
I was inside the Senegal to Mauritania border, end of the day and when I saw the headlight washer coming out of the bumper, with the car locked, I decided to remove the, thought to be, fuse from the fuse box on the engine bay, drivers side.

This ended the headlight washer problem but it also kept the engine from turning...
I guessed that the fuse would not be the one for the headlights washer so I put it back (the headlights started working by themselves again), but I was not capable of driving the car towards the exit of the border, the engine would not even turn and the car wouldn't start, no matter what.
A friend towed it out of the border...

At first I thought that the fuse might be misplaced, however it was not and it was (it still is...) OK.
Maybe we have some terminal out of place, let's check again but nothing... The car was not dead, only it didn't wanted to start the engine...
Every electrical system was working flawlessly, but the engine...

Looking at the START/STOP button, it turned green upon foot on the brake, so no malfunction here;
I noticed that the 4LO light was flashing and the engine light was on but had none on the gearbox position (P R N D S) so I think that the ECU didn't recognized the gearbox lever position, therefore inhibiting the engine from starting.
Moving the lever from P to R it did light up the reverse lights, but still no dashboard indication on position (pic for reference).

I have disassembled the entire fusebox in the middle of the desert (Mauritania) and put it back together, however I haven't found any issue, broken cable, broken connection, whatsoever... The car started the engine after that and everything worked fine, no 4LO flashing lights, no engine light ON, P R N D S lights perfectly normal and the car drove perfectly until I turned the engine off, 1000kms later...
The next day it was, again, malfunctioning, the engine wouldn't start, 4LO flashing and engine light ON...

Unplugged 4 white plugs (inside the fusebox), plugged them back and the engine started (normally, with the START/STOP button).
Travelled about 2000kms, stopped the engine and in the next day everything was normal...
Travelled the last 2000kms back home but somewhere in between, once stopped, the engine got back to not functioning, 4LO flashing, engine light ON, even after unplugging and re-plugging the 4 plugs on the fuse box...

Called for road assistance (was already in the south of Spain) but before they arrive and after waiting a few moments, the car went back to normal and the engine started, always with the START/STOP button...

Once home, went to a TOYOTA dealer, talked the technician through all that happened (took the fuse off, put it back, unplugged 4 plugs, put them back, etc., etc., etc.) but the guy didn't found nothing, the car is perfectly fine and it starts the engine like if nothing ever happened...

My biggest concern is, of course, the lack of confidence in driving the car because I don't know why this happened, if or when it will happen again and what should I look for, replace, whatever to fix this once and for all.

I bought and built the car for some OVERLANDING trips, it has a lot of money invested on it (OME BP-51, DAKAR ZERO's, ARB long range fuel tank, snorkel, drawers, fridge, compressor, ECOFLOW power source, microwave, BMW front seats, DONALDSON's airbox, 12.000lbs winch, rear wheel (custom) carrier, RTT, FOCAL and MOSCONI sound system, full Avery Dennison with PPF wrap, you name it, for giving up on this, plus selling the car with a known issue is not my deal, I would never be capable of passing my problems to others without their consent and knowledge so, please, try to help me out because I would really appreciate some advice, some ideas and some technical information. The problem looks like it is only inside the fuse box (never touched it again..) however I'm open to suggestions, testing and whatever you think would be positive for solving this issue.

 

[lx200inAR]

I would start by checking the ignition circuit for the ECU. There is a section in the FSM for it. The integration relay (part with 4 fuses just above the white plugs you were removing) is an important part of that process. Possibly you have a sticky relay, or a poor connection on one of the few trigger wires. There is a 2way “handshake” between the ignition circuit and the main ECU. So there are a few circuits to check there.

I recently had to do some repair work to the main harness that goes along the firewall. I mis-spliced one of the ignition trigger wires, and my failure mode was very similar to yours. The main difference was I had no check engine light. I did have no start with green start button light and no transmission gears in display.

 

[pmrosendo]

I would start by checking the ignition circuit for the ECU. There is a section in the FSM for it. The integration relay (part with 4 fuses just above the white plugs you were removing) is an important part of that process. Possibly you have a sticky relay, or a poor connection on one of the few trigger wires. There is a 2way “handshake” between the ignition circuit and the main ECU. So there are a few circuits to check there.

I recently had to do some repair work to the main harness that goes along the firewall. I mis-spliced one of the ignition trigger wires, and my failure mode was very similar to yours. The main difference was I had no check engine light. I did have no start with green start button light and no transmission gears in display.

Thank you very much for your reply.

When you say "There is a section in the FSM for it", what does FSM mean? I'm sorry for asking, but I really don't know...

I was thinking in ordering and replace the 4 fuse module near the 4 white plugs, I've read somewhere that sometimes those can have issues and it doesn't cost more than 150€ (something like 150US$) so it's something to do.

Part# 82641-47020

The other part that can be problematic is the fuse rail under the glass, those are not acessible and not replaceable but the entire unit is and it's something with similar cost to the first module so I can give it a try, once I start to disassemble and check the entire fuse box connections, relays, fuses, plugs, etc.

Part# 82620-60050

Nevertheless, I'm still open to other ideas, because this will be fixed, resolved! There has to be a cause, there has to be a bad connection somewhere in the fuse box, I had 10.000+ kms of Sahara expedition, the first 5.000 kms were very hard, through mud, snow, rocks, sand and a lot of corrugations, not to mention that speed kills in this environment but with 300 to 400 kms/day we really had to push a bit and this (not only...) is the end result...

 

[lx200inAR]

Thank you very much for your reply.

When you say "There is a section in the FSM for it", what does FSM mean? I'm sorry for asking, but I really don't know...

I was thinking in ordering and replace the 4 fuse module near the 4 white plugs, I've read somewhere that sometimes those can have issues and it doesn't cost more than 150€ (something like 150US$) so it's something to do.

Part# 82641-47020

The other part that can be problematic is the fuse rail under the glass, those are not acessible and not replaceable but the entire unit is and it's something with similar cost to the first module so I can give it a try, once I start to disassemble and check the entire fuse box connections, relays, fuses, plugs, etc.

Part# 82620-60050

Nevertheless, I'm still open to other ideas, because this will be fixed, resolved! There has to be a cause, there has to be a bad connection somewhere in the fuse box, I had 10.000+ kms of Sahara expedition, the first 5.000 kms were very hard, through mud, snow, rocks, sand and a lot of corrugations, not to mention that speed kills in this environment but with 300 to 400 kms/day we really had to push a bit and this (not only...) is the end result...

View attachment 3840241

I wouldn’t bother with the main fuse. Nothing in it moves and if part of it wasn’t working you’d know.

It’s possible to remove the integration relay without fully disassembling the fuse box. But you may have to separate it enough so that you can get the wire connectors on the integration relay loose. It has two larger connectors and 1 connector with a large wire that feeds the power for the 4 circuits.

If you have a relay issue, it’s almost certainly going to be the integration relay or one of the ECU/FI relays.

The FSM is the “factory service manual”. Available online from Toyota for rent in 2 day increments or there is a thread here on how to set up an offline version on a laptop for free. The FsM clearly outlines how to test the ignition circuit systematically.

 

[kcjaz]

Not sure this will help you but here is a thread with a spreadsheet that helps finding relevant fuses.

2008-2013 Fuse Location Spreadsheet and Wiring Diagram PDF

I had some recent struggles with wiring issues that I've been able to resolve with help of people here. As part of trouble shooting my wiring issues, I put together a combined and searchable PDF of all of the wiring diagrams. I find this useful when I'm looking for something but don't really...

forum.ih8mud.com

 

[pmrosendo]

Not sure this will help you but here is a thread with a spreadsheet that helps finding relevant fuses.

2008-2013 Fuse Location Spreadsheet and Wiring Diagram PDF

I had some recent struggles with wiring issues that I've been able to resolve with help of people here. As part of trouble shooting my wiring issues, I put together a combined and searchable PDF of all of the wiring diagrams. I find this useful when I'm looking for something but don't really...

forum.ih8mud.com

Thank you!

I'll sure look into this.