Aftermarket Catalytic Converter...or Toyota

[wandering chef]

If your inspection is not past due, there's no harm in letting the CEL go a little longer if you want to wait for your OBDII reader to come in check the codes yourself or get some live readings if you want some personal proof.

I'd be hesitant with taking it to a 3rd party shop outside the state it's registered in, if they don't use OEM parts. They SHOULD (theoretically) get you to where you're not throwing any codes or have any monitors unready, but they can't inspect it and pass you.
You may fix it where you are and it all looks good, then you go back to where it's registered for inspection and still fails, but the shop that did the work is out of state, hassle hassle hassle, etc.


I can't answer on one cat or both, but some Googling should let you know.

Thanks again. I'm going to wait for the reader to come in and I'll do a little check myself. Hopefully it arrives on time and I'll read some of the data myself today. I'll need to do the emissions test next year.

Regarding the 3rd party shop, it's in the state where I'm currently get emissions testing (MD allows you to fax in emissions results if the car is out of state). And the cats they use should hold me through a few more years (will check if the parts being quoted are OEM grade or aftermarket).

 

[wandering chef]

Just an update on the situation:

Got the OBDII reader last week and read the code: P0420.
(Using the BAFX OBDII WiFi reader and using OBD Fusion app to read and display the readings)

Spent time graphing the rear O2 sensor voltage, which does fluctuate between 0.7V and 0.1V, with the idle voltage sitting closer to 0.7V-0.6V, and drops in the voltage whenever press on the throttle (using MAF data to identify throttle activity). Read in many other places that low voltage corresponds to lean fuel mix (or high oxygen content) and that properly functioning cats typically do not vary. The drops in voltage whenever I press on the throttle seems counterintuitive since I'm putting even more exhaust through the cats and should theoretically run a higher voltage sensor data (if my cats were truly underperforming) and lower voltages read more often whenever I'm idle.

I think there may be a small exhaust leak letting O2 into the system based on this behavior. Thoughts

New update (Nov 27, 2018): The other shop tested if there was a leak or if my sensors were crapping out. No leaks in the exhaust and the A/F and O2 sensors are reading well. Looks like I'll be replacing the cats (a few months from now). Thanks for the back and forth y'all.