1997 Mercury Cougar MIL light on

According to what I can find you have a malfunction on the heated circuit of the O2 sensor. If all the voltages are good with the O2's thens what it is saying is that you need to replace them. Hope this helps. If you need any more just ask.

"If all the voltages are good with the O2's"... can you clarify what you mean by the above quoted statement that was in the answer.

Ok sure have you checked the voltages at the O2 sensor with a digital multi meter? If not then I will look up the wiring diagram and such and walk you through that so we can determine that the O2 sensor or sensors are bad. Thanks

No, I have not tested the O2 sensors, some instructions would be helpful.

Ok now there are 4 sensors on you car and you will need to check them to see if the heated wire is getting power. Sensor 1 on the right side exhaust manifold check the red wire with the white stripe. Sensor 2 left side exhaust manifold check the yellow wire with the light blue stripe. Sensor 3 is at the rear of the engine in the exhaust pipe check the white wire with the black stripe. Sensor 4 also in the rear of exhaust pipe check the check the tan wire with the yellow stripe. Now you will need to use a paper clip to back probe the connector at each o2 sensor one at a time and then start the engine to see if the wire has power. If this checks out ok then we will look to the reference wires next. Let me know what you find and how much voltage is there.