If anyone likes to play around with their OBD reader, I was wondering what a typical / normal value for the Mode $06 Catalyst Monitor Bank 1 (MID $21, TID $a0) value is?

Background: when I first bought my rig this summer, I was getting occasional readings in the low 400's, which was causing my CEL to pop on with a P0420 (max allowed is 352). Was also misfiring badly. After cleaning up the misfire problem (and running some Techron through the tank a few times), I'm currently running around 150. Not sure if it's due to the idle fix, the Techron, or the transition to winter gas (which has more ethanol, and so is more "oxygenated").

Anywho, if there are any techie types out there, I was wondering what a "good" number is, or if I'm still on borrowed time with my cat.

Thanks!

 

My scanner does not show/supports mode $06; other scanner I had in the past with mode $06 failed to detect idle misfire (intentionally caused by disconnecting coil connector).
However, my scanner shows cat temperature, so the good starting point will be to monitor secondary O2S switching (will be easy if scanner can do the graph) and Cat temperature at idle (after 5 minutes with engine at normal operational temperature)

 

Idle cat temp is about 825 F. Highway cruising around 1200 F.

Not sure how to monitor the switching -- I can graph the secondary sensor fine, but the front sensor is an A/F, so I only have the equivalence ratio to graph (or the commanded and / or actual A/F ratio), so it's kind of hard to compare the front and rear switching rates like I could on older rigs.

 

Temperature reading is not looking abnormal (bad cat will be a lot colder on idle)