Engine light on again

Question

P0420 Toyota - Engine light was on. I took my sienna to Pep Boys on 7/25 to have all this done: replace canister. 10/27 My car had a coolant leak, took it to Tires Plus they replaced timing belt. Replace water pump. Yesterday Engine light comes on. Today i took my Sienna back to tires plus and they told me that i had to take it to Pep Boys because it had to do with what they had worked on. Tires plus wants to see the invoice from Pep boys and maybe fix problem and charge them if it has to do with what they fixed. Any advise???

Answer 1

if there are no exhaust leaks or physical damage most likely the catalytic converter is bad of the oxygen sensor is fine. The oxygen sensor will have to be looked at with a scanner that has waveform 

it will have to be looked at.