i checked the grounds for the 02 they are ok adn the o2 signal is ok

but its throwing a code for the o2 sensor heater but im not getting battery voltage with the key on and engine off at the ecu... does this sound like the heating element in the p2 sensor is open or does this sound like a wiring problem

p.s. its a 92 cx (came obd1 but with a 1 wire o2 sensor) and i had to wire the 4 wire myself but its been throwing this code since i wired it up and swaped it

any help / experience appreciated

 

you should have ground at the ECU with the key off and engine not running. At least until the O2 heater heats up.
the O2 sigal from the ECU is ground to turn on the heater, the other side of the O2 heater is connected to ignition power from the group of yel/black wires at the dirver's shock tower.

 

i should have ground at a6? its the orange/black wire that according to the sheet i have is labled o2 heater... and also on my sheet it sais it should have battery voltage with key on engine off

there is no voltage there at all

im starting to lean towards a bad o2 sensor

 

on a P05/P06/P28/P30 and most P72s (OBD1 ECUs) the way the O2 heater works is one side of the O2 heater is connected to the ignition (yel/blk wires at driver's shock tower)
the othe side of it is pulled to ground by the ECU.
So for the first 30sec or longer the ECU will ground the heater control line to warm up the O2 sensor.
After that time the heater control will let the heater rise to 12V.

since you have a CX you had to have run the other side of the heater, where did you connect it to? ground?
if you did it will always show this fault because the ECU expects to see current flowing through the control transistor in the ECU.
If you wired the other side of the heater to ground the ECU will ground the heater control to turn it on, see not current flow and set the fault.
wire the side of the heater that is not run to A6 to ignition power and it should work. (as long as your O2 is not broken)

also the O2 heater should measure somewhere between 10-40 ohms if you have am ohm meter you can make sure it's not bad.