i bought a new o2 sensor for my 4runner. the one on my runner tested out at 6.2 ohms. right below the 6.3 allowed. but with the really bad 12mpg ive been getting im desperate for anything.

the new denso just came in the mail and i tested it. it tested at 6.6..... above what the FSM says. so i dont understand. is it supposed to test higher? i havent put it in yet becuase i cant get the bolts that are holding the old o2 sensor out. they seem to have been welded on and they will not come off.

1990 runner 3.slow

 

What you need to do is to test the 02 sensor WHILE THE ENGINE IS RUNNING.

This means after the engine is warm.. and using a HIGH IPEDENCE DVM (most DVMs are) check to see if the voltage across the sensor is "scrolling".
I think there are pin outs at the test connector.

If the 3.0L has a Vf signal at the ECU (and at the check connector) check to see if that voltage is "steady" at 2.5 v

See FSM for testing procedure details....