Electrical help needed.

2007 4th gen 4WD limited. Son drive it. Going to class he gets to parking and stops and dash lights up, like every warning light there is. Engine still running and temp gauge shows fine. Shuts it off and calls me (~1 hour away). Tell him to first check serpentine belt hasn't broken or come off. It is fine. Restart same, dash lit up like Christmas tree but engine running fine as well temp gauge working and fine. I tell him to drive it the few miles back to where he lives and park it and I'll be over.

Go over with various tools and OBDII reader. Able to clear most codes and restarts but still have a battery charge light. I decide to leave him his mom's 4runner (2006) and risk driving this one home where I can work on it. Bad idea. I did stop at an auto parts place and the confirmed it was charging but just out of caution I shut off the A/C and put the windows down in spite of the 93 degree heat.

I head home and about five miles out the wipers come on all by themselves in super high speed and then a fuse of something blows and I lose almost everything except the engine is running and I still have temp and gas gauge. Car is running fine so I soldier home.

Since removed alternator and battery and battery is good but alternator had both bad charging circuit and bad volts regulator. Replace alternator. BUT, here is where I have questions:

I still don't know what else I may have damaged by driving it with the bad alternator? I when through the fuse box (junction boxes in Toyota manual speak) and identified five total blown fuses.

In engine FB:

10 amp ECU-B fuse
10 amp STOP fuse

Junction box in cabin:
7.5 amp ACC fuse
10 amp ECU-IG fuse
10A Tail fuse

I still don't know what was chicken versus egg and if a short burnt out the alternator of if a bad alternator put out current or volts that popped all the fuses? I have of course also replaced all the blown fuses. What I have not done yet is reconnect the battery and try it. My concern is if I have a short or ground in the system it may just take out the new alternator again? I am also concerned I may have toasted some part of the Body ECU that is intergral to the fuse block under the dash?

I was taking some resistance readings between the positive battery lead that goes to the fuse box in the engine compartment and ground and with the 10 amp ECU B fuse replaced I get zero resistance to ground. That seems very odd and looks to me like if I hook it up I am basically shorting positive and negative battery leads. Can anyone tell me if this is a normal reading with all the fuses installed everywhere and ignition off (battery disconnected)? If I pull that fuse the reading goes to infinite.

I am pretty good with automotive electrical and trouble shooting but just not sure how to proceed here? Also does anyone know if I replace the fuse block / body ECU unit under the dash if the keys / car will need to go to Toyota for reprogramming?

Sorry for the very long post but wanted to provide all the info I can.

 

Follow up: I got up the nerve to connect the battery and see what happened. Good news is four of the 5 fuses that were out before didn't blow. Bad news is the ECU-B fuse in the engine compartment box blew immediately as I sort of expected given the zero resistance to ground reading. So, this leaves me assuming the Body ECU in the interior fuse block is toasted? The truck starts right up and runs fine but of course I still have various warning lights (though fewer) associated with functions the body ECU plays a part in. And still of course also no power to any of the functions off that ECU, A/C, windows, door locks, etc.

So, asking again; has anyone here ever swapped out the interior fuse box and if yes did it have to be programmed or was it plug and play? Any insight would be appreciated.

 

Just an update: First, the answer is no, when you swap interior fuse boxes the integrated Body ECU does NOT need to be coded to the car. It is plug an play.

I have just about finished recovering from my expensive lesson re-learning NEVER drive a vehicle with the battery / charging light on!!!! I assumed it was a dead alternator and that I could drive the distance I needed to on the battery. What I overlooked was the possibility (true as it turned out) that the voltage regulator had gone bad and the alternator was putting out TOO MUCH VOLTAGE. Long story short I am a new alternator, 7 fuses including the main 140 amp one in the engine bay fuse box, a new interior fuse box (well technically the associated B-ECU), a new master door switch (again a circuit board fried), a new AC ECU amplifier and heat control face plate (two more boards fried), and a 4WD ecu board into the repairs. Basically anywhere the circuit got to a circuit board first it fired it.

The good news is I have sourced all the boards / switches / control panels from eBay saving literally thousands of $$ from what Toyota would want for them new. All plug and play and all back to working.

Bad news is I did pay close to $800 to Toyota to diagnose all this and for them to replace the 140 amp main fuse (requires removing and partially disassembly of the main fuse box and made it possible to drive it home after flat bedding it there).

 

Hi, I have almost exactly the same issues. I have a master window switch on the way and in the process of sourcing an HVAC/heat control unit.

When sourcing an ECU-B/interior junction box, does it have to be from exactly the same model as my vehicle? I drive a 2007 4Runner 4.0L V6 Limited. I have attached a photo of my junction box and haven't been able to find one on eBay with the same code/serial number. From what I've found all the 2003-2009 4Runner junction boxes use the same fuses, but I'm wondering if the ECU-B is vehicle specific.

Thanks for your help!