I searched the forums over and could not find this problem in the Sienna forums but did find it on other cars. What cued me that there was a problem was the cruise control would cancel when I put the right turn signal on, similar to touching the brake pedal.
Problem:
When I turn on the right turn signal all three brake lights flash in sync with the turn signal bulb. All other function work normally. When the brake lights are on, the right turn signal does not come on so this tells me it is not a wiring problem but rather a relay or solid state switch. The brake brightness was about 90% of full brightness when the brakes are applied. The problem persisted when the right tail light assembly was removed. I also noted that when the assembly was removed that the plug did not look like Toyota but rather the trailer lights connector. When I removed the trailer connector from the factory harness everything was back to normal.
Solution:
Once the trailer light converter box was found, I solved the problem my clipping the two wires that connect it to the right tail light. Of course if I need to tow, the converter box will need to be replaced. Just posting in case anyone has this problem. Also noted that the tail light fuse had been replaced by previous owner. I know this because they used a mini and not a low profile mini.
Note:
When removing the tail lights, after the two 10mm bolts are out, the light pops out to the side with two metal pins and plastic retainers. Mine were really hard to remove. They were so stuck, I actually broke the fixture removing it and epoxied it back together. When I reinstalled I used silicone grease to lube the pins. I seems like these trailer light converter boxes can cause a myriad of problems affecting ABS, turn, brake and of course blown fuses.
Problem:
When I turn on the right turn signal all three brake lights flash in sync with the turn signal bulb. All other function work normally. When the brake lights are on, the right turn signal does not come on so this tells me it is not a wiring problem but rather a relay or solid state switch. The brake brightness was about 90% of full brightness when the brakes are applied. The problem persisted when the right tail light assembly was removed. I also noted that when the assembly was removed that the plug did not look like Toyota but rather the trailer lights connector. When I removed the trailer connector from the factory harness everything was back to normal.
Solution:
Once the trailer light converter box was found, I solved the problem my clipping the two wires that connect it to the right tail light. Of course if I need to tow, the converter box will need to be replaced. Just posting in case anyone has this problem. Also noted that the tail light fuse had been replaced by previous owner. I know this because they used a mini and not a low profile mini.
Note:
When removing the tail lights, after the two 10mm bolts are out, the light pops out to the side with two metal pins and plastic retainers. Mine were really hard to remove. They were so stuck, I actually broke the fixture removing it and epoxied it back together. When I reinstalled I used silicone grease to lube the pins. I seems like these trailer light converter boxes can cause a myriad of problems affecting ABS, turn, brake and of course blown fuses.
