Thanks for the info, very helpful. Relieved to know that replacing the sensor still has a good chance of fixing this CEL.
Truck has been in CO for most of its life, so lots of salt and mag chloride on the roads that could be responsible for the worn nuts. I thought the front ones were bad...
Reviving an old thread here, but it has relevant info. First post here too.
I have a 99 sr5 CA emission, auto 4wd with 138k. I was getting codes before indicating a bad front A/F sensor (dont remember codes), and I tested the sensor and the resistances were not there indicating a bad sensor...
