electrical issue with stop lights

I do not see any damage to connectors or wiring. Everything inside is in pristine condition. The skid ECU A41 outside connector had some dirt. I cleaned it, but it did not help. I also did not see any wiring damage inside the taillight assemblies.

I asked the dealer to replace the switch. Waiting for a replacement.

It looks like I have a voltage leak from pin 7 to pin 1 when the pedal is not depressed, because I always have 12V between Pins 1 and 2, and that is causing the lights to stay on. I should be getting <1V with the pedal not depressed.

 

Maybe, but I tried two other batteries and a jump starter with much higher CCA, and the stop lights problem does not go away.

 

This is beyond frustrating. Got the replacement switch. Excited to fix my car in 10 minutes, I quickly realized that the new switch did not fit into the metal holder. How can this be, I thought? New switch is identical to my original one. Upon close inspection I noticed two tiny seams on a plastic wingnut on the replacement switch. These seams were on the wings that locked the nut into metal holder. They prevented the nut to be pushed all the way through the metal plate. Not a big deal, I thought. Just lightly sand these wings and be done. Or even re-use the old nut. So I thought... A few light touches with a sandpaper, and the wings are perfectly smooth, the switch is installed correctly and... the white pushpin is fully stuck in the closed position (as if the pedal is released). A few curse words came out. But the car now isn't drivable. At the very least, I have to put the old switch in. I get the new switch out, toss it on a counter, and the push pin comes out. Then I try to push it in with my fingers. My old one is very smooth with nice and uniform spring resistance. The new one is like grinding sand. I pushed it in, it is stuck again, again, and again. Tried to spin the pushpin. Found a position where it is almost kind-of smooth. Installed it. The lights blinked a few times and then went off. The lights stayed off for 10 hours and a few short trips. Late in the evening they started blinking again.

Now what? Buy another switch from another dealer? Is there a reputable aftermarket switch I can use instead of the Toyota branded one?

 

Here is the package. It is the correct part number. The seams that prevented installation could be from manufacturing when plastic parts are molded as a matrix and then cut into individual pieces. This should not happen with "high quality OEM parts", but now it is not a big deal. The bigger problem is the lights are still not ok.

So, the new switch (i.e #3) is much better than the other two (my original and the first one dealer sent me). The lights used to stay on pretty much all the time. Today I drove ~200 miles. The lights never came on (when the car was parked). After I came home, the lights stayed off for ~3 hours. Then I noticed lights were on. They stayed on for, maybe, 10-15 minutes, then started blinking again, and now they are off for about 2 hours. I did not touch the car or even walked nearby.

The last switch (#3) is mechanically defective, because the white pushpin gets stuck if that pin is rotated a certain way.

I can't leave it like this because one day I will get stuck 100 miles away from home with drained battery.

 

Both replacement switches I tried, I bought from the official Toyota dealership, also listed on parts.toyota.com. The only markings on the switches are: 1) my original switch: 310-3G33 2631; 2) the switch I returned: 310-4X49 00008 3; 3) I don't have a photo of the switch currently in the car, but the marking had a letter "Y". Is there a way to find out the manufacturing date?

The lights are off and not blinking at the moment. They were off for the last few hours.

Another observation. I wrote above about problems with internal fan not stopping and the key not working. When the switch is not "acting up", there are no problems with the key or the fan. Everything works as it should.

 

I described initial symptoms in my first post. The internal fan is the ac/heater fan inside the cabin. Everything is stock, no upgrades. It is model one (i.e. barebones). When stop lights are on, the electronic key works intermittently, and the fan does not stop when ignition is turned off unless I press the "off" button first. It looks like an intermittent short between pins 1 and 7 in the switch, which somehow affects the operation of the fan and the key through main ECU.

I traced the wires. No damage, no vapor, all connectors are fine. Lights blink on a dry sunny day too. The lights were off all night last night and all morning today after a couple of short trips. If I go back to my old original switch, the lights come right on and stay on.

 

The lights were off all day today though I haven't done anything to the car. I hope that the new switch will finally work correctly after initial rough "break-in". If the lights come back on, I will film how the fan stays on when the car is off, stops when the brake pedal is depressed and starts again when the pedal is released, all with ignition turned off. I could not believe it either when I saw it.

 

The stoplights have been fine so far, but the switch gets stuck. Almost got stranded last night 100 miles away from home with the switch pin stuck inside and shifter blocked. Had to drop the brake pedal a few times to release it. It was stuck again today in the morning. Ordered another (3rd) replacement. So annoying....