Got my buddies LT1 running today and could only get it into closed loop by sending the Right(passenger side) O2 sensor to feed both of the of the inputs to the ECM.
Tried both inputs from the Left (driver side) O2 sensor, but that doesn't work. Swapped out 2 other O2 sensors on the left side....no haps. The only thing that worked was feeding both ECM inputs from the Passenger side O2 sensor.

Now, I suppose that not one of those 3 O2 sensors I tried on the driver's side was good....but why would it go into closed loop by feeding it from the single O2 sensor on the passenger side?

Any ideas?

 

You mean you installed a new o2 on the left side and tried again? how is the ground or connection where the o2 screws in? if it is excessively dirty / rusty it could be preventing the sensor from grounding , did you weld in your own o2 bungs? or are they factory?

 

I have heard of O2 sensor drivers being burnt out of the PCM. Do you have another to try? A scan tool would allow you to monitor this.

 

But this one just got refurbished. It all works well, it's just odd that it goes into closed loop only after I hook up "One" O2 sensor to supply both inputs into the PCM.
The bungs are factory into a cast iron exhaust manifold. Tried applying various ground straps to ensure a good ground. Not suspecting it's the grounding system.
I'm wondering if it matters at all since it's a 93 LT1 and I believe it's bank fired anyway? Was the bank firing supposed to be controlled from it's individual separate side?

 

I can't see it being a burned out sensor input circuit, since it's definitely making use of the signal from the right side sensor when it's hooked up to the left. However, it *could* be a bad connection in the wiring harness; I'd check all four wires going to the sensor and make sure they're doing what they should be. Assuming that the 93 O2 sensor connectors are the same as 94-95, which is the schematic I have on hand, position A (tan wire) should go to the PCM's negative oxy sensor input, position B (purple wire) should go to the PCM's positive oxy sensor input, position C (black wire) should go to a good ground, and position D (pink wire) should go to switched (i.e. ignition) power. If it's staying in open loop even when the engine's been running a while, it's probably the signal wires, since the exhaust gases would (I think) get the sensor hot enough to operate, although maybe not quite as accurately as normal.