I have a 2005 Camry with approximately 56K miles.I have had it regularly maintained and never had anything unexpected show during those maintenance visits. Recently, at about 55,400 miles, the check engine light came on. I took it AutoZone and theypulled the P0420 code from it. I have done a little researchand it seems that the problem could be with the 02 sensors and/or the catalytic converter itself. Mymain question is how truly serious is this? The car runs terrific; no noises, no smells,etc. I know I'll have to get it fixed before my next emission test, but that isn't till February. Is it okay to drive till then (providing no other problems or symptoms crop up)?

On another note, I tried to reset the CEL by pulling the EFI fuse but it didn't seem to take. Do I also have to disconnect the battery? I'd like to see if this is a one time thing or something more permenant.

 

The cars emissions troubleshooting system has no way to directly test the CAT for efficiency and thus reports this code. The system checks CAT performance indirectly. P0420 usually means there is a problem with the 02 (A/F) sensors, their circuits (wiring) or the CAT. The exhaust system has 02 (A/F) sensors before and after the CAT. The signal outputs from the two sensors are compared by the ECU to determine the efficiency of the CAT. If the signals are of the same amplitude, the ECU triggers the code. Meaning there is a problem with either of the sensors, their wiring or the CAT is operating below efficiency. There are specific trouble codes for the sensors but none to indicate the CAT is bad. If no other codes are indicated pointing to a 02 (A/F) sensor then running down the problem is harder without doing some kind of diagnostics. The Toyota dealer or any shop equipped with the right type of equipment can determine if it is a sensor or CAT problem without guessing.
The CAT is typically covered under a mandated EPA extended warranty. The period is something like 8yr/80K miles, check your cars warranty info. If the CAT is the issue, you want to get the problem fixed before the warranty expires. Toyota OEM CATS are very expensive. The warranty period on the sensor is typically 3 years or 36K.

The car is OK to drive but you MPG and performance may suffer.