PO 420 2000 Camry

So got four new injectors installed, finally passed my inspection, got rid of the PO-301 engine light. Running great. All readiness monitors fine. Two weeks later get a PO-420 “Catalytic System Eff. Below Threshhold (Bank 1)” I’m thinking that when the guy replaced the front little muffler–had to cut out old one with sawzall and weld the new one in–the vibrations and/or debris might have plugged the catalytic converter down the line That’s the best scenario. I do notice some kind of vibration underneath. I know they should check for exhaust leaks, O2 sensor etc. Could it also have been traveling on some gravel road–vibrations,potholes etc? I’d really like not to now have to buy a new converter.

The code to the computer is from one or more O2 sensors sending a signal to the ECU that the readings it’s getting isn’t within spec.

It may be the cat OR…one of the O2 sensors is bad. There are procedures to tell if a O2 sensor is bad or if the Catalytic converter is actually bad.

The unburned fuel which resulted from the misfires (P0301) could have fouled the O2 sensor(s) and the catalytic converter. You could, actually, pull and inspect the O2 sensor(s) for carbon fouling. A scan tool, in the right hands, will show the performance of the O2 sensors ---- so, there wouldn’t have to be any guessing.

thanks guys. First step–now that I have my handy MacTools ET-80 was to write down all the freeze frame info then erase the PO 420 and see if it comes back again. Then I have to find a mechanic I can trust. Does this freeze frame data mean anything to you? (I hope these figures stay in format so they’re readable.)
Fuel SYS1 CL
Fuel SYS2 N/A
Load PCT 80
ETC (cent) 100
ShrtFT1 (%) .8
Long FT1 % 0.0
Map kpa 80
Rpm (min) 2221
VSS (kmh) 97
IAT 16