P0420 Chevrolet -

Question

i have change the oem one with a universal one from autozone two weeks later the service engine light came back on cannot get rid of it when i scanned it it tell me that the are two monitors that are not complete evaporative system and secondary air system incoplete

Answer 1

2 monitor incomplete, when you start the engine on a cold start listen for the secondary air pump to come on. If it comes on you should be able to complete the secondary air injection. The secondary air  monitor can only run at a cold start up.It would also be a good idea to check for any pending codes,