I have a 2000 Toyota Tacoma 4cyl automatic, 97k miles, with a check engine light on. I had codes read and they said to replace the oxygen sensor. I didn't realize there were 2 sensors, now I'm trying to figure out which is the problem. The auto parts guy didn't say which it was when selling me a single sensor. I physically found both sensors, one on either side of the catalytic converter. Limited youtube search suggested failed senors will fail a continuity test. When I tested both upstream and downstream sensors, neither failed continuity.
Upstream sensor 127 ohm, downstream is 135 ohm.
The new sensor is 9.5 ohm.
Does this mean that downstream is worse due to higher resistance? And the upstream is ready to fail since it is so close?
I called the auto parts place and they did not save the code, so I'll have to go back to have it read again if I want to know which sensor the OBD says is bad.
Also, this is not a spark-plug style sensor, it mounts via two studs and a gasket. The nuts holding the original sensors on are shot, splitting and ready to crumble. Is there an easy way to know what size these are so I can get some replacements for the install? When I get them off, they will be in pieces, so I won't be able to bring one with me.