I have a 1990 toyota pickup I picked up two weeks ago to give my powerstroke a break for the winter. Anyways it runs fine has a check engine light. My friend owns a shop and we tested it and it says o2 sensor. But here's the catch the book says I should have 2 sensors and I only have one that I see before my cat. So is my truck expose to have 2 sensors? Please help and yes it's a 22re

 

California trucks had 2 o2 sensors. (tougher emissions)

Just replace the one you have.