rear is faulty
needs to pulse above .3 otherwise it will throw out a code - as u can see it rarely goes above .2
the one on the left looks lime the mixture lambda and looks to be pulsing normally between .1 & .9 volts - the rear looks lazy but it should be closer to .5 - .8 volts as when the cat warms up it idles around that voltage
below .45 is lean
above .45 is rich
