I didn't get a voltage reading at either brake light assembly connector
except 0.1 at one lead on each side (driver and passenger). The fuse
is good and I inserted a new spare just to make sure. I didn't find
any other loose grounds.
A few older posts mentioned a yellow "lamp failure sensor" box in the
trunk near the top of the driver's side wall. I removed and opened it
up and the circuit board looks good (no burned marks). Puzzled, I did
a little more searching and found more info in this thread:
http://www.automotiveforums.com/vbulletin/t80545.html
Check out posts #23 by decible and #32 by G.I.JER. My circuit board
has the exact same problem shown in the photos. The soldered
connection at pin #12 (looking at soldered side of board) has gone bad
(appears to have melted just enough to be slightly disconnected or
shorted). It's small and barely noticeable and since there are no
other clues such as burn marks, I didn't even see it until I reviewed
these photos and inspected the board a 2nd time. To test I held a
jumper wire between the solder on the board and the wire going to it
(from a tiny white diode or resistor located just below the connector),
and this made all 5 brake lights work. I resoldered the connection and
it works fine. I'm guessing the problem was caused by the loose ground
wire on the brake lamp socket causing the board connection to heat up,
which I've now fixed more permanently (all it takes is for this screw
to get slightly loose from normal vibration to create enough heat to
melt the plastic around the screw). I'm so glad I didn't have to
replace the pedal switch! Thanks for your help!
By the way one of the best features of 87-91 generation Camrys is the 4
big tail/brake lights stretched across the entire trunk except the
license plate. Newer models have fewer or smaller lights so they are
harder to see and might be more prone to rear collisions. I especially
dislike the narrow 97-01 generation lights, which look like they are
falling asleep. The current generation is better.