I failed emissions in Illinois due to p0420 and p0137. I had my cat stolen about 2 years ago and replaced with an aftermarket. Steps taken so far: 1. Replace front 02 sensor 2. Replace cat with another aftermarket from Amazon which claims to be "EPA Compliant" https://a.co/d/4RuKuUn 3. Drove for at least 100 miles between highway and city, and never got any of the 3 Monitors to "Ready" on my OBD2 scanner. 4. OBD came up with p0137 5. Took to a hybrid shop, they were about to swap out the rear 02 sensor but when I said it was an aftermarket cat, they said it would never pass inspection. Am I doomed to buy an OEM Cat? Is there hope if I put in a new rear sensor? How the F#+$ can I get the monitors to come online? This is a 2007 with over 300K miles. It runs fine but won't pass emissions, so I can't renew registration, and keep getting tickets while it's parked on the street (wish I had a garage or driveway).
LOL for $69 that generic cat can't have much of any catalyzing materials inside it. You may not be doomed to buy an OEM, but you could at least try an aftermarket that isn't complete potato. Yes, it's much more expensive than a potato but still cheaper than OE and more readily in-stock.
For one thing, the P0137 has to be addressed. That's a problem with the oxygen sensor, and until that code is fixed, the monitor for the catalyst performance isn't even able to run; the functioning O₂ sensor is needed for the catalyst monitor test.
Talk to your DMV about this problem usually you can get a pass for a year or something like that I didn't in Western Massachusetts one time.
Fix the rear 02 sensor first (post cat) You'll still get a check engine light which will not let you pass emissions. How strict is the inspection in your county? a spacer will eliminate that p0420 code if they don't inspect it. Have a reputable muffler shop install an aftermarket cat for you, it doesn't cost that much. I have a friend who let the shop install the cat for $150 and it's still working for more than 4yrs..
The new cheap non CARB aftermarket catalyst might pass emissions once. Then it is a matter of weeks or months for the P0420 to come back and stay.
+1 to Chapman If the ECM thinks there's a problem with the downstream O2, it won't try to run several monitors. Could be the O2 sensor, or an exhaust leak (like at the new cat connections), or even something wrong with the A/F sensor. That cheap cat MIGHT be completely useless, but you can't know until the O2 problem is repaired. You could read the diag procedure for that code in the service manual, then perform some tests. Or keep firing the parts cannon- might just hit something. Posted via the PriusChat mobile app.
