I have an AFS 75 four wire Oxygen sensor supposedly off an LT1 Trans Am. I was wondering which of the wires is the signal? There is two brown (assuming the +12v and gnd for heat), a purple and a white. Is the extra fourth wire just another ground?

Also, what causes the sensor to wear, time or mileage? The sensor came off a car with 9,000 miles on it but it is about 10 years old.

Was wondering because i want to put it on my GTA.

 

 

Thats what im looking for! Any idea if this thing is still good after 10k miles and 10 years?

 

Sorry, the only way I know to check a O2 Sensor is on the vehicle. It has to be at operating temp before you can determine if its good. You also have to follow the service manual due to a couple of different types of heated O2's. If you use the wrong testing procedure it could kill the sensor. There are other things which can also kill a O2. Several years ago we (Automotive Indrustry) were having problimg with dead O2's. It turned out to be that RTV was the culpret.

Bill

PS Now we just need a spell check