Re -checked the integrity of the HEGO signal wires to the ECU 60 pin connector and HEGO ground wire (orange wire with loop connector from pin#49) from the ECU connector to its attacment at the intake maniflod bolt/stud. Connections and continuity test OK for both. From this I conclude that the HEGO signal and ground circuits are OK, just that I don't get a voltage reading above 0.0-0.1v and no switching at closed loop idle. I'm concluding the exhaust gasses are very lean for some reason(s) I cannot discover, and the HEGOs are driven to reflects this.