91 244 with lh 3.1 - I keep getting a code 2-1-2 (missing/faulty heated o2 sensor signal). I replaced the old sensor with a bosch 13953 spliced into the existing wires but the code still comes back. Car runs very rich and stumbles, idles poorly.

Probing between the still connected single wire connection and ground gives a steady/unchanging reading of .54v

Disconnected the two heater wires and checked for the voltage being supplied to the heater - only got a reading of .02 volts I am assuming it should be getting a constant 12v . Where does the power supply for the heater circuit come from - I assume the ecu? If so what pins - want to work back and find if its a broken wire. The tip of the old sensor was black and sooty so I assume it was not heating up either.

Also, could I just connect the heater wires to a good, ignition switched, 12v power source or does the ecu look for a completed heater circuit?

Thanks for any ideas!

Jim