I have a quandary and I need help. I'm a mobile tech and my customer has a 97 Camry. The cat converter monitor will NOT become ready and he has driven hundreds of miles. I had a 94 Camry and never had this issue. I boroscoped the cat converter and it's perfect, not even any carbon on it. The oxygen sensors are showing the correct data on the scan tool in live data. There are no DTCs for the cat like the dreaded P0420 or any codes for O2 sensors. I'm completely mystified. Anyone have any ideas?

 

The 1994 was much more rudimentary in its emissions and CAT monitoring system. Thought the converter could become 70% inefficient before it failed to pass an ECU check.

For readiness, Toyota requires certain conditions be met beyond having a working system. These are not listed in the service manual.

The CAT efficiency is checked after warmup and then engine at 2500-3000 RPM for 3+ minutes.

It appears others have had this problem, and the links below provide info on what they did;

Please.....97-01 Drive patterns to reset Catalytic system monitor. | Toyota Forum (toyotanation.com)

toyoyta computer readiness test - Search (bing.com)