Toyota Repair: p0420 code and p0300 code, toyota camry solara, 2001 toyota camry solara

Question
QUESTION: Why when I start my car in the morning it sometimes shakes for about 10 sec like its going to stall. Then the rest of the day the car runs fine? I only got the p0300 code once and I researched that. There was a tsb out for my 2001 toyota camry solara 2.2 engine stating that if the p0300 code mil dtc comes out that the ecm has to be replaced and reprogrammed. Am I wasting my money by buying this computer. Also regarding the cat code. It states bank one. I changed bank one sensor afr sensor. Should I change bank one sensor 2 first before buying the actual cat. I'm very frustrated because I just hope the money I'm spending on a new ecm will fix my problem

ANSWER: I have read the service bulletin and it seems that following the instruction as outlined in the bulletin will take care of the p0300 code. the 420 code is a catalityc inefficiency code, you are not getting any O2 sensor codes so it's not necessary to replace them, replace the ecm and the spark plugs, clear all the trouble codes, the cat converter code can be triggered by the p0300.

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QUESTION: Why is toyota telling everybody that the cat has to be changed and then when the cat is changed the ecm light comes back on. I was just thinking. That being that I already changed bank one sensor 1 sensor that maybe bank one sensor 2 has to be changed. I'm afraid to go to the deaaler because they would just tell me my cat is bad. Its weird the the p0420 light will come on while I'm driving then when u erase the code the code sometimes doesn't come back for a month or so.it seems now imgetting a p0420 a lot bank1. I fully tuned the car up sparkplugs wires fuelfilters idle air control valve motormounts new shocks and struts timing belt new waterpump. What next

Answer
But you're not getting a code that would indicate a bad O2 sensor or A/F ratio sensor, first fix the problem that you are actually getting a trouble code for. The reason for the check engine light taking a long time to turn back on is because the computer may not run a monitor on the cat for a while and the cat efficiency may be marginal so it could be intermittent, the dealer can run a monitor report that shows if the cat monitor ran and completed or passed/failed, they can also test cat efficiency and print the results but in the end I'm afraid that the cat will need to be replaced.