Does the i930 read the four O2 sensors separately and give the the output voltage on each?. Can you watch the system go from open to closed loop and detect what sensor is bad ? I have an 0420 code from the ELM327 (catalyst) and not sure if it's upstream O2, down stream O2 or the converter.. Thanks

 

The ups are diff technology to the downs. Ups are current-based, downs are volts-based. Standard OBD can read all 4, even an elm327.

Forgot to say - it'll probably be the cat itself

 

I think you were right there JagV8 ..I changed the downstream O2 out because I was told by Eurotec main mechanic (where I took it for an inspection) the sensor was the culprit with the ck engine light..oh well. The light stays off for a day or so then comes back on and I get P0420. _