I have a 97 f-150 lariat 4x4 with a 5.4 liter , and upon scanning the underside of the truck I have 2 sensors before the cats and 2 sensors after the cats. Could someone please help me with this?

Thanks ....Scott: confused:

 

There are O2 sensors before and after the converter to allow the computer to determine if the converter is doing its job. If there is no difference between what the O2 sensors shows before and after the converter--then the computer knows that the converter isnt doing its job--and causes a "check engine light" to go on. All OBDll vehicles ( newer than 1995) have at least two O2 sensors--and V engines have usually two for each bank of the engine.

 

Hey Phoneman,
Thanks for the explanation. I read in my owners manual that the o2 sensor should be changed at 100,000 miles and I bought my truck at 97,000 and it now has 134,000. This could be expensive having to replace all four of those puppies. I think I'll just wait till they go bad and replace as needed.

Thanks again phoneman

Scott