I know this is an old thread but I wanted to post because I had the same problem (no tail lights, all bulbs and fuses are fine) and I wanted to share my solution.
From what the dealership told me, if you have a 1988-1991 Camry, and you look in your trunk, on the driver's side, behind the carpeting on the side wall - you will find a small yellow box about the size of a pack of cigarettes. Disconnect that box from the wire harness, and use a flathead screwdriver to carefully open the lid. You will most likely see an obvious area that is black and chared a little left of the center marked with a printed number on the circuit board, like 1 or 2. There's the culprit!
You can either pay Toyta some un-Godly ammount of money to replace this POS part from the 80's, you can try to hunt one down in a junkyard for $5-$30 plus gas and time depending on where you find it, or you can make the repair yourself. Luckily the fix is easy as pie. . .
Firstly, if you are looking dead on at the wire harness plug the diagram goes something like this according to something I found on the internet:
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: 01 03 05 07 09 11
: 02 04 06 08 10 12
: Pin 1 (Green) to Tail lamp Fuse ..voltage w/lights on
: Pin 2 (Lite Green) to Tail Lamps ..
: Pin 3 12v
: Pin 9 to Brake Pedal .. voltage when depressed
: Pins 11 & 12 to Brake Lights
: Short/Splice 1 & 2 for Tail lights on when lights are turned on.
: Short/Splice 9, 11, & 12 together for brake lights.
: Other pins are used for the lamp on the dash and power for the sensor.
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*note: I, personally, don't have a Pins 09 or 11 on mine, so I came up with a slightly different solution. Read on.
OK! so all I did was remove the yellow box from the wire harness, and then I took a conductive sliver of thin metal and used it to bridge Pins 01 and 02; the two green ones that account for my tail lights.
Now, low and behold I had tail lights again! Only problem was that, in my case, I no longer had break lights. Ack! That won't do, so what I did next was simply insure that the bridge I made for the green (tail light) wires was short and non-intrusive. Then I opened up the yellow sensor box I removed ealier, got some needle-nose pliers and removed (twisted until they came out) the pins from the circuit board connector where it would have plugged in to the tail light pins, since I already have my metal bridge there on the harness. Once that is done I can reconnect the sensor box to the harness. You should now have tail and break lights. The only thing you won't have from now on is an indicator letting you know if a tail light blub goes out since you have essentially bypassed the sensor for your tail lights. Personally that doesn't bother me though. It's a free fix and it's really easy. I hope this helps someone
- Dustin