| Decoding the codes and the troubleshooting
David Mc; you could be onto a heck of a save here. I looked at the manual and from the schematic and using my background in electrical troubleshooting AC/Heat units these O2 sensors are four wire gizmos. 2&4 contain the variable resistor circuit which likely reads exhaust temp to comunicate via two connections to DME and 1(Brn htr grd)&3(Red/Wht to fuse box) contain what appears to be a heating element circuit. This circuit seems to follow an electrical path to the DME(1) and (3) power (This particular code indicated "heater" so this may be the corcuit that is causing the code . This goes along with your insight about a short or open circuit.
OK try and follow along with me here...
From the schematic all of these are contained in a box together which if I test continuity of the wiring at the connector and find any loss this will probably mean a new sensor as it would stand to reason that these wires are not separated and are probably self-contained in a harness ala the apparatus itself.. If someone knows different please tell me. The other loss it appears I need to check for would be of t he wiring outside of the connector between the DME and the connectors. From all the pictures diagrams I have seen in The Bentley manual(thgis one seems like one circuit from each O2 sensor pre and post CATCONV and online these four sensors all seem to feed the DME and power. Any further insight would be apprciated as this trouble shooting seems time intensive? Wish me godspeed on this trek. | 
