Greetings,
Was just over at a friend's house taking a reading on his LT1 using my Autoprom. The LT1 has 2 oxygen sensors. Well, one of them was never going above ~450v, and the car never went into closed loop. We swapped leads, and then the opposite side sensor would never change, we checked continuity to the ECM and it appears the lead is good. At this point it would seem that the lead is fine, the sensors are fine, and that ends up making us think that perhaps the ECM is shot. I then burned him a chip with VATS turned off (just to eliminate the pro-made chip as a problem). Well, the problem is still there, one O2 sensor doesn't react, the sensors seem fine, the leads seem fine....do y'all suppose that the actual ECM could be shot?
Another question:
Does the LT1 need both O2 sensor sides to be "good" prior to going into closed loop?

Thanks,

jcj

 

I would assume that both O2s have to be fully functional and not stuck around .450V to enter closed loop. Id double check all the leads and also check them against ground to rule out any shorts or ground faults. If all that looks good, then its likely a hardware fault inside the PCM.

 

The one side that appears bad just hangs out at ~450v. When we swap the O2 sensor leads the opposite one looks bad. Continuity is sat from the sensor connection to the ECM. Even opened up the ECM to check that the connection at the terminals to the circuit board had continuity....that's sat. Looking more and more like the ECM, eh?

I'm usually playing with my 730 ECM and it only has one O2 sensor; it goes into closed loop as soon as that one looks good....

I gather that the LT1 needs both O2 sensors to look SAT for it to go into closed loop?

Does someone if that is definitively yes?

 

You could also make a voltage divider with a feed from 12V and apply it to the O2 sensor wires to the ECM (with the O2 sensor disconnected) before pulling the ECM. That would tell you if the ECM is bad.