Mab, to comment on your last post first, that is an ingenious invention, never seen anything like that over here before, will look into it. To the best of my knowledge the dump couldn't be got via EOBD port, think it has to be done at ECU using a break out lead - watching an ECU on ebay that is the same, its only £30 so perhaps worth buying to experiment on.
Coming back to the signal issue and the confusion between us regarding it. In the course of testing heater circuit work arounds I've made some interesting finds so far when it comes to the signal circuit.
From the beginning of the expeiment (when I first removed lambda sensors and replaced heater with a coiled length of element wire) the signal wire has been left floating. Interestingly in this state the line idles as 0.435v, as read serially using a scan tool. Whats more, it picks up on noise in the engine bay, which causes oscillations, of say 0.015 in either direction of the baseline.
Here is the strange part, when I access the ECU using the Vauxhall (GM) option and read DTC's, errors are now present for both heater circuits B1S2, B2S2, and then errors also for the signal side of things, can't remember the code, and my notes are at the unit but the description reads along the lines of 'o2 sensor signal - no activity detected'.
Ok fair enough - thats a clear error, but when I access the ECU under EOBD, only the errors for heater circuit are listed.
Hence I would like to sort the heater side of things, to find out if whether or not the signal error on GM side would cause MIL, and then if they did cause MIL, I would continue to try ways of defeating the signal side of things. Its as much for enjoyment and research as it is for practicality.
Kim: Thanks for posting back, that makes more sense now.