Ok guys, I ran a test on my truck awhile back with the autotap and I have a bad 02 sensor but I couldn't tell which one it was from the autotap.

So now I have the exhaust all out and I was looking to find out which one of these is bad. is there some kind of test I can run with an ohm meter or voltage test, I don't know.

thanks for any help guys.

 

Yes.

Using a Digital Multimeter or DVOM (high impedance only).

Set it to check Ohms resistance.

Chiltons/Haynes books show you which wires are the signal return, the PWR, GND, and heater PWR/GND. It also tells you which ones to probe between. I believe you check resistance between SIG RTN and PWR.

I can't remember what the tolerance is for the reading, but I think it's 2 - 50. Most I've checked have been 4-5. Refer to the procedure listed in the book for exact numbers and wiring.

Don't use an analog meter, or one that is not high impedance, or you will mess up your sensor.

Hope this helps.

 

Disconnect one of them and run the diagnostic test again. If it still shows only one is bad, you unplugged the bad one, if it now shows both are bad, you have unplugged the good one.