First off thanks to the guys who posted with the help on code po136 & where the banks are located , anyway I met a guy who said dont be ina big hurry to throw away $$$$ on new sensors ! they last a long time he said take then out have a look clean them good & try them again ... they were the back ones & easy to remove they were not all that dirty so I buffed them with a fine wheel buffer , sprayed them with some throttle cleaner , cleaned the wire conectors good also , put a dab of antizeez on the threads ..... reinstalled the senors which have over 100,000 miles & she is running like new no more codes ... I KNOW THE BOOKS SAY NEVER SPRAY ANYTHING ON THEM ! well it worked , so just thought I would pass it on as its an easy fix & that guy who gave me the idea said 90% of the time they just need a cleaning & has seen cars with 250,000 miles with the original 02 sensors , so much for the adds that say change them every 75,000 miles ............ PS the auto-store guys were of O-help couldnt even find the right ones for my car & prices for $53 to $73 long leads short leads & other nonsense so thats why I gave cleaning them a try , hope this helps ....