my 99 toyota camry LE is out of control!!

hi everyone, I bought the 99 toyota camry in 2004, and it was running
smooth till a year later where I had to replace the vapor pressure
sensor at the dealer. However, starting in May this year, the
maintenance signal kept showing up, and i ended up brought it to a
body shop and...

5/15 : replace the vapor pressure sensor (again!!)

7/6 : in late June, the signal light was on, and did a fuel
induction service (a 3 part induction cleaner)

7/24 : a day later, the light was on again, the shop people found a
leak in the evaporative emission ctrl canister and installed a hoses
recommended by toyota and also an O-ring on the air inlet port on the
canister

8/1 : brought it to the dealer service center and they said
something wrong with fuel cap and the charcoal cannister was broken.

8/4 : the guy in the body shop said the fuel cap is totally fine but
he did replace the charcoal cannister for me

8/10 : after i picked up the car and drove for less than 20 miles, the
maintenance signal was again, on, brought it back to the body shop and
they turn it off for me.

8/11: someone did a hit and run on the car, and the signal was ON

9/7 : when i picked up my car and drove for less than 30 miles, the
signal was ON again.

today: i took the car back to the repain shop yesterday and they reset
the computer, however, when i drove to work today, it was ON again!!

although the dates are kinda spread apart, but i promise, that signal
light came back on the next day i picked up my car!! even the guy from
the body shop told me people from other body shops had no clues what's
going on, ( it's a business center with several body shops) they did
everything the computer said and the car should have no problems at
all.

i really have no idea what to do now, i've spend almost $1500 on it
within these months, and i also don't know should i bring it back to
the dealer and trust their service anymore since they are famous on
"ripping off" their customers and as i mentioned above, the fuel cap
is good in shape while they said something was wrong with it.

is there anyone know what's going on with my car and what should i
do??? getting a trade-in or another car is currently not possible
since i just graduate from college.


THANKS!!!!

> Do you have access to an OBDII code reader? They will lend you one for
> free at some auto parts stores in the US, or you can buy one for $150 or
> so. Read the codes and tell us what they are. Some codes do not
> require immediate attention.

I meant to reply on this message board, but i think i click the wrong
link and it sent to your email. sorry about that. but yea, the code is
PO446, got it from the dealer invoice and it's also the same code the
guy from the body shop found every time he diagnosed the car. besides
the services already did, what else could go wrong? will it expode all
in a sudden due to some unknown clotting or overheating or anything
since i've basically driven it with the light on for months?

thank you