Hi,
I have bone stock 93 C1500 5.7L TBI with a 16168625 ECM/PCM and BDJZ std code.
I failed emissions and was looking thru Tunerpro datalog to see if I could see why.
I noticed that I'm dropping out of closed loop when sitting at hot idle due to the O2 sensor changing to "not ready".
I checked coolant sensor, cleaned up grounds and confirmed in datalog I'm @ 90C when this happens.
It appears it happens when O2 sensor doesn't fall below 400mV when in closed loop. Possible the other criteria is over 700 mV. Can't tell if it's an either or both from trace.
I've possibly never replaced the O2 sensor and assume I have a "lazy" sensor from reading/googling - so I'm going to replace it.

I was curious if anyone knows the specific criteria for the "ready" status of the O2 sensor?
I've read that the other two criteria to be in closed loop is a coolant temp and a engine on time criteria.
If anyone knows those also, I'd appreciate it. I've seen many different coolant temp criteria - I'm assuming it may be different for different engines.

also
I noticed that if I cold start and just let it idle it never gets into closed loop. The temp comes up to about 90C and @ 10 min it's still in open loop.
I can see the O2 sensor slowly rise with temp from around 450mV to 550mV with little noise as INT is not changing.
If I blip the throttle hard so force a change in O2 below 400mV then it gets into Closed loop and INT changes and O2 changes as I'd expect.
It seems this is normal behavior assuming the O2 sensor ready criteria of changes under 400mV / over 700mV is correct. Is this also right?

Thanks for help. perhaps not needed to verify O2 sensor is bad but curious about how the system works.
Ed