Downstream o2 sensors running rich

[albany9044]

I have a 98 Eddie Bauer with the 5.4. I've always got really bad gas mileage like 11 -12 mpg and decided to look into it a little further to see if there was some kind of issue.l n it does have the 3.73 LS rear end btw. Anyhow, when hooking up a scan tool both of my downstream o2 sensors, (bank 1, sensor 2 & bank 2, sensor 2) appear to be running rich. The reason I am thinking this is because they literally just hover around .7 volts and don't really do much switching at all, and I find it interesting that it is on both banks. By the way It's not throwing any codes, and it has almost 232k on it. Thanks in advance

 

[69Hcode]

The downstream sensors just see if your cats are working. They shouldn't affect how it runs.

 

[69Hcode]

Mine are turned off. Runs great and passes emissions.

 

[stamp11127]

Proper running cats should generate 4.5v at the downstream cat. Check the upstream o2 sensors voltage output. You should see the readings going up and down. If they have failed the ecm will be in open loop which is a rich fuel trim.