o2 sensors

[wills4runner]

I have a 91 4runner the check engine light came on last week. I checked the code #21 O2 heated sensor now, my question is. How many O2 sensors the 91 4runners came with? and the second is ther a way to know which one is the one that is not working?

 

[fourwd1]

It depends -
What engine do you have?
Is it a CA emissions vehicle? (and if you're not in CA it doesn't mean it's not CA emissions).

 

[wills4runner]

it is a V6 and i dont think is a CA. can sombody help?

 

[Hunner]

Have you checked to see if you had 1 or 2. i'm assuming the CA's have 2, one before the cat and 1 after. my 95 3.0 had the one before the cat