Toyota Sequoia 2001, 4WD, Short term fuel trim B1S2 and B2S2 fixed at 99.2% ?

I check data by Autel scanner for my Toyota Sequoia 2001, V8, 4.7L engine as per photo attached. No thing wrong with Short term fuel trim and Long term fuel trim of Bank 1 and Bank 2, value under 10%. Good up stream Oxygen sensor Bank 1 and Bank 2 with data moving up and down from 0.1V to 0.8V . Down stream Oxygen sensor B1 and B2 at idle speed fixed about 0.1V. When I rev up the engine, value of down stream O2 sensor change to 0.8V ( Down stream O2 sensor not dead). The only strange value is Shorterm fuel trim B1S2 and Short term fuel trim B2S2 fixed at 99.2% at all the time when Idle or rev up the engine. Please help me to explain this case. Will this effect my gas consumption? Do I have a bad Catalytic converter?

Thank you for your help.

Hey Maila! Those trim values for the downstream sensors are completely normal. They have zero weight on the fuel calculation, and can be safely ignored.

The long answer is that the PIDs themselves are part of the OBD2 standard, and legally required to be there, whether the vehicle makes use of them or not. But when the scanner asks the car what the value for that PID is, the car has to respond with SOMETHING. So, the default value is 99.2%.

It's a goofy PID - I've looked at Global data on hundreds of different cars, and never seen one that makes use of them. Even vehicles that have downstream fuel control don't change those values from 99.2%. :silly:

Dear Tyler,
Thank you for your reply to my question. I learn some information from you. Have a good day.