I have the Chilton manual for the 1995 Bonneville, In the book it says you can check the resistance of of terminals c and d and if it should be between 10 and 15 ohms at 79 degrees or the sensor heater is faulty. I checked mine and it is 4.6 ohms. Should I swap it outwith a new one ?I am having a hard time gettting the scan tool for this car. It is running rough and has a irratic idle. THis is the sam o2 sensor that was in when the previous engine blew up and filled the exhaust with oil and coolant. ANy thoughts would be greatly appreciated. Thanks

Forget the diagnosis. If the heater were blown, it would only affect the idle quality for the first 5 minutes or so.

If the sensor is at least 50k miles old, or you don't know how old it is, or it was ever exposed to oil or coolant, replace it.