2010 Toyota Tacoma IG1 2 Fuse Blows – Battery Goes Dead

This 2010 Toyota Tacoma came in with the complaint that the IG1  No2 fuse would blow sometimes. The IG1 NO2 fuse is located in the interior fuse box behind this panel.


After pulling the door open the whole unit can be lifted up and off of the hinge detents.


The interior fuse box legend with the location of the IG1 NO2 fuse being pointed to.


The actual 10 amp IG1 NO2 fuse in the interior fuse box.


I will admit that this is the first time that I have encountered this exact problem on this vehicle so I had a little bit of a learning curve as to what all is on this fuse circuit. Turns out that almost every system is affected when this fuse blows. According to the customer most of the warning lights on the dash would come including the ABS, Traction, Brake and SES lights. He also stated that the a/c and power windows would stop working. Eventually the battery would go dead while driving indicating that the alternator was not charging either. The owner stated that replacing the fuse would last several days to several weeks when the problem first started. It had gotten worse and the fuse would sometimes blow as soon as it was replaced and the key switched back on. As luck would have it it had not blown in several days before being brought to my shop. There was a code P0500 stored in history.

I looked through wiring diagrams and consulted several resources looking for a lead in what could be blowing this fuse and found that there are quite a few others in pursuit of the same answer. My first inclination was to the overhead compass above the rear view mirror since they have a history of not working and loose resistor floating around on the circuit board. The unit in this truck was working properly and light bumping with the heel of my hand made no difference.

I started my visual inspection under he hood and looked in all of the usual places around hot exhaust and sharp metal brackets but could not find anything.

I was inspecting the harness connector at the alternator when I spotted this. A wiring harness very close to a bolt head and bracket with a slight rust discoloration near it. You cannot really see it in the following picture …


…. so I went and looked through the inner fender opening to get a better look. See that tiny bit of powdery rust between the bolt head and the wiring harness. That was the evidence I was looking for.


After unplugging the green harness connector from the alternator I was able to move the harness away using a long screwdriver. Now a shiny spot was visible on the metal bracket.


Pulling the harness further away and looking at it from the topside showed heavy rub and rust marks on the harness tape.


I did not get any pictures because of the tight working area but I did use a test light and confirmed that there was power on the wires inside that rusted spot with the ignition on and a good IG1 NO2 fuse installed. I removed that fuse and the power went away proving that this was indeed a shorted wire on that fuse circuit.

I proceeded to remove the split loom and tape from that short section of wiring harness. After that I wiped the rust residue from the area and could see the damage on the light green wire. Enlarging the next image makes the damage easy to see.


The best way to repair this wire would be to remove the entire harness from this corner of the engine. Repair it and then re install it. A ton of work so I decided to go a different route. After removing the white internal terminal retainer I was able to release the internal terminal latch. This allowed the terminal and wire to be pulled free of the connector body. I then slid heat shrink tubing over the terminal and down the wire to the insulation damage. The internal wire was okay. Only one strand had been nicked. I reassembled it all including a new piece of split loom that would also cover the area better that the original had.


No to make sure this never happens again. Using a pair of slip joint pliers I was able to bend the edge of the steel bracket down and compress it onto the aluminium housing it was attached to. That by itself gave an extra 1/8″ to 3/16″ of room between the harness and the bracket.


Wanting to do a little better I split a piece of hose and placed it between the harness and the bracket.


I then squeezed in some sealant to act as a glue to hold the rubber wedge in place. The customer agreed to allowing the vehicle to mostly sit for a day to let it cure out.


As many of you already know my motto is to start  inspecting/testing and stop guessing. This repair is a definite example of how to do that. As many inquiries as there are about this issue, I am sure this is not the only Toyota Tacoma that has this exact problem.

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