I have a 94 850. I recently installed two generic o2 sensors and and now I keep getting codes 131 and 137, ( low voltage front/rear sensor) This happens after driving fifty miles or so after clearing the previous codes.

I did get code 141 (open circuit o2 heater) but I respliced the connecters and eliminated that. That's a 12 volt circuit.

My thoughts are because the sensors operate with such low voltage >.9 volt that perhaps the extra resistence of splices causes a Voltage drop in the circuit thus causing the illumination of the CEL.

If this is the case, why doesn't the light illuminate right after it gets to operating temp and enters closed loop?

Any insights would be greatly appreciated.