Installing a 3-wire Heated Oxygen Sensor


This is primarily advisable if you have headers.  Headers tend to cool the exhast gasses down, which in turn can affect Oxygen Sensor performance.  To combat this, a self-heated sensor can be installed, to ensure proper operation regardless of exhaust temp, and also provide shorter times to closed loop operation.  I will spare you the details on actually installing the sensor, since it doesn't take a brain surgeon, just a 7/8" wrench, sensor socket, or crowsfoot and some of your time.

The reason for this article is to explain how to properly wire it up.  First, you will need the parts. I perfer to use AC Delco parts.  The quality is unsurpassed.  Also to ensure proper installation, and easy replacement in the future, it is reccomended that you purchase the "pigtail" or connector w/ leads, so that the sensor can easily be plugged and unplugged as needed.

The part numbers for these two items are:

3-wire Heated Oxygen Sensor:  25176708  GM List: $109.00

3-wire Weatherpack Connector: 12126012   GM List: $29.34


You will notice the sensor has two white wires and one black.  The white wires can be interchanged, polarity does not matter.  Once must go to a good clean ground, either on the body or the engine block, and the other must go to a 12V switched ignition source (Power w/ the key in the "RUN" position).  Many people tap into the MAF power wires if you have a MAF sensor, but any "hot" wire in RUN only will work.  It can't be HOT all the time, or you will drain your battery.

The black wire goes to the stock PURPLE wire that originally went to your one-wire Oxygen sensor.  This is the signal wire to the ECM.


Here is a schematic: