Camry :: 2005 Solara Engine Light Has Been On And Off

Since I've owned the car, which i got in December of 2013, the engine light has been on and off. The previous owner, who drove it off the lot in 2004, was a family member who took it to a mechanic multiple times. Multiple mechanics said it was the gas cap. I replaced the gas cap back in February 2014. The engine light still comes on and occasionally goes off.

Here's some information I've gathered driving the car since then

Straight highway mileage tops out at 28 MPG. Only city/town driving yields about 19/20 mpg, so the gas mileage is okay

Last weekend, I drove around on maine roads for the whole weekend, spending about 90% of the driving time doing 50+ on roads. The engine light successfully went off and stayed off for the longest period of time since i've owned the car.

The rust situation on the car is extremely minor, except for some rusted fittings. Frame rust and general surface rust is non existant except on certain pieces that can be replaced (struts, tie rods, ect) However, there is one piece that looks shitty, which is the spacer between the exhaust header out of the engine and the engine block.

The code the car puts out is either a catalytic system failure or catalytic system operating below threshold. There is a new catalytic converter in the last 3 years, so I highly doubt that's at fault (not to mention the engine light manages to stay off for the yearly inspection and it passes emissions no problem).