[mwebb]

Originally Posted by Carwhisperer

How does one test a wide band o2 sensor without hooking it up to a controller? Is it possible with a dvm? From what I've read it looks like it is not possible without an oscilloscope. Is this true?

can not be done
do you mean AFR sensor ? even a scope can not be used .
How 5-Wire Sensors Work (Tech Edge)

with a scan tool testing an OBD2 system ...
you can follow STFT , or EQ ratio graph it if you can . STFT or Eq ratio should swing around 3 to 5 % and center on zero .

quick test is to see if STFT will settle on zero during a steady state . if no
almost always the AFR sensor is skewed or biased high or low , but an exhaust leak upstream of the AFR sensor OR after the cat or a fraked rear 02 sensor can cause rear trim to influence STFT .

an aftermarket AFR sensor in your hand
can not be tested .

the heater resistance can be tested and compared to a specification
but , that is about it .
resistance testing is about as useless as mudflaps on a sledgehammer