My 2010 4Runner with no electrical modifications keeps blowing the 10A Tail/Stop lamp fuse. There are two fuses for these lights: one under the hood(10A Stop/Tail) and one near the pedals in the driver's side instrument panel fuse block (10A Stop/Tail). The one near the pedals is the one that keeps blowing. When the car is cold, with a new fuse, both the stop/tail lights function properly. I drove around until the engine got warm and then pulled over when I noticed my lights went out. The fuse blew again, and the only working light is the passenger side brake light. The drivers side brake/tail and passenger side tail all are out. I swapped the bulp+twist on socket between the sides and still the passenger brake is the only one working with the fuse blown. Replaced with a new 10A fuse on a warm car. Tail lights working, Passenger side brake working, drivers side brake NOT working. Swapped bulb+socket again, still drivers side brake only light not working with fuse and bulbs still intact.

Hi mbshaw88,

I've looked at and provided the wiring diagrams for your truck. Chances are, you've got a blown stop/parking lamp/License plate bulb with a dangling filament creating your trouble. I would remove each bulb, one-by-one with a visual analysis, paying close attention to the filaments within the bulbs! Drive the truck (carefully) without any of these bulbs in their sockets and see if the problems go away!

Then examine the bulbs that you removed. Upon examination, you'll likely see the X-circuiting in one of the bulbs. When you've determined which bulb is blown, remove it and return the others. Replace the blown bulb with a new one from your local 'Auto-zone' parts store, and test the stop lights again... the trouble should be resolved! Please be sure to let us know how you make out!

In the wiring diagrams below, I've traced the Tail-relay HOT circuit in pink (wire #5), the power source circuit (from the Alternator) in Blue (wire #6), and the GND circuit (WH/Blk stripe) in yellow (very pale); for easy viewing! "see below":



Let us know, 'Best to you',

rig

Thank you!
I'll post an update tonight to see if pulling the bulbs still results in a blown fuse.

EXCELLENT mbshaw88!

I would like you to remove ALL of the rear bulbs...e.g., brake lamps, parking lamps, license plate lights, turn signal lamps...etc. This will tell us if the trouble is originating in the wiring or the bulbs; but I'm leaning towards a bad bulb with a busy broken filament, robing a power source from another circuit: which would explain why a passenger-side lamp stays on with a blown fuse!

rig, cheers!

Tested everything last night step by step and somehow I couldn't get the fuse to blow. The only thing I noticed was when I placed the license plate bulbs in they didn't turn on right away, I had to push them in a little more then they turned on. Drove around about 20 minutes total with no fuse issues, all lights working.

This morning checked the lights before leaving for work. Got to work an noticed my lights weren't working, and the fuse was again blown. All

Here's the summary

Okay mbshaw,

Have you removed ALL the rear bulbs, including the license plate bulbs and rear side-markers? This will help you isolate the trouble! If the fuse still blows, you'll need to start unplugging rear harnesses from the "Driver-side fusebox!

Let me know what you find from these vital tests; I'll help you with the 'step by step' procedures.

rig, cheers!

During my previous driving test table, yes all rear bulbs were removed during the first step, then reinstalled step by step thereafter. The white cells with the dotted lines meant the bulbs were not installed during that test. The only thing I didn't know at the time was that the front side marker lights are also on the same TAIL fuse circuit.


However, I was able to make some progress after reading more of the wiring/connector diagrams

I removed:
- front side markers x2
- tail/brake x2
- license plate light x2
- 10A TAIL Fuse

Measured Resistance between Green and Black/white pins on O12 & O13 tail light connectors and license plate bulb connectors. Reading non-zero resistance at all connectors so there is a short somewhere, as there should be no connection to GND with all those removed.

After reading schematics, found Junction Connector O19 in the rear pillar and disconnected. This would isolate each bulb so I could find which had the short. Remeasured each connector and now reading no continuity for both tail/brake connectors. Still reading non-zero resistance at license plate connector. So the short is somewhere between the license plate lights and O19 junction connector!

Good job mbshaw88,

I just have one question: "did you disconnect the Center brake light" from the circuit; if overlooked, it will create resistance when the circuit is tested?

rig, cheers

Yes I did unhook the center brake LED before doing the continuity tests. I ended up cutting the #6 wire at the O19 junction Connector (the green wire going to the license lights) and haven't had a blown fuse in 2 days. I figured I could splice it back together once I find the short at a more convenient time, but I needed to drive home in the dark and needed those tail/brake lights!


Thanks for the help!

LOL! okay,

Are you absolutely certain that one of your "License plate bulbs" aren't shorting with-in... seems suspicious that the wiring would be faulty (having never been modified), and those bulbs have nothing at all to do with it! ("Yes, PLEASE put your safety first")

rig

I currently do not have either of the license plate bulbs in their sockets. And I also have the #6 green wire cut at the O19 Junction connector. All other bulbs are back in in their respective sockets and working correctly. When I take a resistance reading at each license bulb connector (black/white & green wires) I get a non zero reading. This circuit should be completely open.

It is really odd with a stock wiring setup but I'm going to take the liftgate panel off this weekend to see if I can find where it's shorting out

Sorry to rekindle an old thread, but I'm not used to posting on forums or trying to tackle electrical problems. I have a similar problem as described above in 2015 4Runner SR5 with no modifications.

All turn signals, brake lights, reverse lights working. Tail, license, side marker lights not working. First replaced fuse and lights worked briefly before fuse blew again. Took out license plate lights, observed black on bulbs, replaced bulbs and fuse - blew fuse again. Removed license plate lights and front side markers, inspected tail light assembly connections and left connected - fuse blew as soon as i switched from DRL to parking/side marker position on steering column.

Any insight for the electrically challenged would be much appreciated!

Too bad the OP didn’t post with his final resolution. I would guess he took off the rear hatch trim panel from the inside to gain access to the license plate lights. Probably found a shorted or damaged wire. There’s a lot of shock and vibration in there from slamming the hatch.

Are you the original owner? Did everything ever work or is this a sudden new problem? Are all the light bulbs the original incandescent or did any get replaced with LEDs?

Did you take out the license plate bulbs, front side markers bulbs, tail/brake bulbs, replace the 10A TAIL Fuse, then turn on the headlights to see what happens? Did the TAIL fuse blow?

You could try repeating some of the OP’s steps to remove all those bulbs and the fuse to measure the resistance to ground at each pin of the license plate bulb sockets. Maybe you too have a shorted wire there. Good luck.

Thanks, Eletroboy. I'm second owner, but have been driving it for over three years without issue. The only thing I've changed is driver side headlight and tail light assemblies (after hail damage), but have been driving with those for several months. I did take out all those bulbs and still blew the fuse.

My 2010 Limited 4Runner would not start the other day. When I hit the brakes and pushed the start button it would not turn green (stayed orange), would not start, and no response. No clicking, no noises, and the instruments remained dark.

When I hit the start button a second time, all accessories were enabled and functioned fine.

I suspected dead batteries, bad FOB's, one of the safety interlocks, stoplight switch, and several other things, but all were dead ends.

The Short story: I found out how to Bypass the Lockouts and get it started, and then finally traced it back to a shorted brake light wire.

Also confusing is that when I started it in Bypass Mode, the anti skid light and ABS lights were on.

What did I do first:
- Checked the main Battery Voltages, recharged, and confirmed 12.7v, and lots of starting power available.
- tried both FOB's, tried holding them close to the start button, checked their batteries, confirmed that they would open and close the remote locks from +20feet away.. etc.. no FOB problem's

By chance I read somewhere about a possible safety interlock start bypass No explanations, no descriptions on how to, but by luck I found out it is real, and here is how that works:

- Touch / Hit the start button once with no foot on the Brakes (normal start)
- Hit the start button a second time (accessory mode) but do not release, and hold it down for 15-20 Seconds
- The T4R's will now start and bypass all the electronic safety lockouts.
- You can not shift out of park at this point because the shift lock is still engaged
- Pry the small plug out located in the console beside the shift lever to access the manual override, insert a small key or screwdriver and push the button, shift to reverse, drive etc as per normal.

NOTE - You can now drive the car, but what ever is wrong electrically is still there, you have just overridden many of the safety Features, and this is an Emergency Procedure Only! It also helps trouble shooting as you can start you car!!!!

Now on to the Electrical Problem!

I checked all the fuses located in the panel under the dashboard. No Faults were found. I checked all the fuses in the engine compartment and found the 10 amp Stop Fuse was blown. I replaced this, tried to start as normal by depressing the brakes, hitting the start button, and no start again. The fuse was blown again!

I was now looking at some sort of short, malfunction in the ABS or other safety systems, and or the brake system.

In each step of trouble shooting I would basically replace the fuse, Test normal start conditions, and when this did not work, I would start the car using the bypass start method to confirm I had not messed anything up, and worked through each safety system disconnecting, bypassing and isolating them.

I suspected the brake Switch because of the lockout situation and this is the first thing in the circuit downstream of the fuse so I disconnected it, checked, tested various situations of unplugged, and finally replaced this as it was only ~ $40 from the local Parts store.

Same thing, and each time I tried a normal start sequence, I had same conditions, no start, no green light on the start button, the fuse was blown again, but it would start in Bypass.

At this point, I bought 20 x 10 amp fuses to start isolating the problem.

I suspected the STOP Relay in the engine compartment fuse box. Tested, checked, tried several configurations, and determined it was working ok.

I disconnected the wire harness connections to the ABS ECU located in the engine compartment, drivers side, on the side of the brake system, Replaced the fuse, no start, same conditions.

Next was the shift interlock - I removed the center console by screwing off the shifter handle, then puling up on the side of the silver console cover to pop it off (about 2 minutes of work, and thank you Utube for how to do that one).

This exposed the wires for the shift interlocks, parking brake connects etc located under the consol. I disconnected the interlock wires for the shift lever suspecting a possible short there. Went through all the same things, and still blowing the fuses.

So now I am down to brake lights and systems.

I did not suspect them first because each time I tried to start the car and hit the start button I was blowing the fuse. I thought one of the interlocks was shorting when it was powering up and they also receive power signals from the stop circuit.

I reality, what was happening is that in order to start the car, you must put your foot on the brakes. With each new fuse, each time I tried to start, The first thing is power was being applied to the brake lights, and shorting out.

Easily verified, I replaced the fuse, touched the brakes, and fuse was blown. I did not have to try starting the car, it was just a read herring that when that fuse blows, you can not start the car. it had nothing to do with any of the safety systems.

So I disconnect the tail light harness from the left and right side in the rear of the car. Touch the brake pedal and the fuse did not blow.

One by one, plug in the left brake lights - OK, Plug in the right Tail Lights fuse blown... Problem isolated in the right Tail Light assembly

With my right tail light assembly disconnected, and a new fuse in place, I could "normally start the car" and everything else worked fine.

After removing and disassembly of the tail light assembly I found that one of the wires running to the brake bulb had been pinched between the mounting screws, and the frame. This must have happened when I had some body repairs done, they replaced it, and it was just marginal for it to last for 6 months while I drove around all winter.

I could see the pinched wires, and exposed copper that was grounding out I small piece of shrink wrap, some heat, and "proper reassembly so no chance the wires got pinched and after 2 days of head banging... I now have a car that starts normally, and working brake lights!

PS - I cant even imaging what the Dealership might have done or charged.