So this is one thing that I have no idea about. A car I'm bringing to smog has passed the sniffer test but either 1) failed because of CEL on: ELM327 with Torque said P0420, or 2) clearing the code and cannot / have not yet finish the OBD2 CAT and EVAP drive cycle. I talked to another smog guy and he said that since about 5 years ago they are starting to chase after the drive cycle and CEL, even if the sniffer test pass it would be a fail now.
The car in question has about 20 years, 150k miles, with original O2 sensor (I assume), as far as I can tell it uses 4 wire so it is a zirconium narrow band O2, instead of the wide band 5 wire O2 that cost $120 or so. A rock auto Denso upstream will cost around $50 shipped (needs 2 for a V6), or a Walker will cost about $30. A Cal Cat would probably be about $300 and the car isn't worthy of a new cat (it will go to Mexico or Africa instead).
Let's say the old O2 is lazy by now, and let's say both upstream and downstream are narrow band O2, does the upstream get worn out earlier than downstream? and therefore I can assume that the downstream is fresher than the upstream, and I can swap them and make them work better?
Or do both up and down stream get worn out the same way? and therefore I should invest in some new upstream O2s?
The car in question has about 20 years, 150k miles, with original O2 sensor (I assume), as far as I can tell it uses 4 wire so it is a zirconium narrow band O2, instead of the wide band 5 wire O2 that cost $120 or so. A rock auto Denso upstream will cost around $50 shipped (needs 2 for a V6), or a Walker will cost about $30. A Cal Cat would probably be about $300 and the car isn't worthy of a new cat (it will go to Mexico or Africa instead).
Let's say the old O2 is lazy by now, and let's say both upstream and downstream are narrow band O2, does the upstream get worn out earlier than downstream? and therefore I can assume that the downstream is fresher than the upstream, and I can swap them and make them work better?
Or do both up and down stream get worn out the same way? and therefore I should invest in some new upstream O2s?