Heated 4 Wire Oxygen Sensor Conversion
*If you prefer not to do this yourself, I can build and supply a conversion kit for you (NOT including new O2's) with better pics and detailed installation instructions for $70 shipped. You can email me for ordering instructions.
I'm going to apologize ahead of time about the poor quality of the pictures. My digital camera doesn't have a close focus function, and I did the best I could to clean them up with what I had.
Parts needed (two of everything):
GM 4 Wire Oxygen Sensors, Part Number 25312184, $37.00
GM 4 Wire O2 Harness, Part Number 12102741, $15.39
In-Line Fuse wiring kit
30 Amp Fuses
Red 14 Gauge Electrical Wiring
Black 14 Gauge Electrical Wiring
Weatherpack electrical splices (the heat to seal kind)
Circular Wiring connector (for the ground)
Convoluted Tubing
Zip Ties
Electrical Tape
Wire Strippers/Crimpers
Anti Seize Compoud
For us 93 F-Body guys, our old school single wire oxygen sensors can become a problem with the addition of headers. For the oxygen sensors to properly function, they need to be H-O-T, approximately 600 degrees F. With shorty headers this isn't really a problem, but moving into a mid length may make it a factor, and is almost definitely a player if you have long tube headers. With my own personal experience, my stock one wire oxygen sensors would bounce in and out of closed loop at idle with my Arizona Speed and Marine Headers. Doing this conversion will keep your car in closed loop at idle and will also give an added benefit of allowing the car to go into closed loop much quicker, due to the reduced time it takes the oxygen sensors to reach operating temperature.
To start things off, I used the above drawing to sort of map out exactly what I was going to do. I used this as a starting point, and ended wiring up seperate lines for each O2 sensor, but I digress. We'll come to that.
To start things off, you need to remove your old oxygen sensors. Disconnect the battery, get the car up in the air and get under there with a 7/8" wrench and get those bad boys out. Once that's done, don't throw them out just yet. You're going to need part of them.
Referencing the above pic, cut each of your old Oxygen sensor wires off in the general area shown where my leatherman is positioned. *The reason you're doing this is because you're going to splice the weatherpack connector into the new 4 wire harness, thus preserving the integrity of the cars harness in case you ever find a need to switch back to the one wire sensors. Plug and play this way.*
Strip off enough of the covering to be able to get a good splice, and using the weatherpack splices, connect the old O2 wire with the "B" wire of the new four wire harness, as shown above. If you have trouble identifying which wire is which on the new harness since all four wires are white (I initially did), plug it into the new O2 and look at the O2 end of the weatherpack connection. One side of the connector is marked A-B-C-D and you can trace the proper wire out. Once you have the wires identified and the old O2 wire spliced in, you should be able to identify which wire is which by position and using the schematic. If not, a piece of tape and a sharpie will fix you right up.
Once the O2 plug is spliced in, you're ready to move on to the power and ground wires. Simply cut the approximate length needed for each wire (I over estimated at 8 feet, can't be too safe and it's better to have more than not enough), and splice one end of each into the appropriate wire. Once that's done you can use the convoluted tubing to finish off your loom.
Looking at the above looms, you'll noticed that I taped them up a lot. I basically started at each end and where the O2 plug sticks out, and then anywhere from 4-6" between taping. I just wanted to make sure the wires weren't going to protrude and possibly get severed.
Get back under the car and install the new O2 sensors. Be sure to use anti seize on the threads. Now you can hook up the wiring harness' and route them as you please.
On my car, I routed the driver side from the O2, over to the inside of the strut tower, and zip tied it to another electrical harness. I then routed it forward along the bottom of the strut tower, then went straight up by the Cruise Control Module and then between the brake lines, under the ABS unit, and into the open area (where a CAI would be if installed). I found this way to give me the best clearance and most security from the headers on my car. On the passenger side, I zip tied the harness along the main vehicle wiring harness from the starter and went forward and OVER the K-Member. Once to the front of the K-Member I made a 90* turn to the driver side of the vehicle, and zip tied the harness along another part of the electrical harness, and followed it over to the driver side strut tower, then followed the driver side O2 harness up by the cruise module and between the brake lines over to the fuse box.
Ok, now that your wires are routed and tied in place, you can trim the power and ground wires down. Find your in-line fuse kits, I used the ones available at any auto part store that take a standard spade fuse. Connect one end of the fuse kit to the red power wire for each O2 harness.
Most, if not all, of these kits come with wiring in to and out of the fuse box, but not enough to fit from the opening under the car fuse box to the other end where it will be connected to the switched power spade. You'll have to add some wire to the open end of the fuse kit. Just add enough to leave the O2 harness fuse about 4-6 inches from the car fuse box. Once you have that wired in, go ahead and put a fuse in each in-line holder and close them up.
So, now that the looms are done, you can move on to figuring out where exactly you're going to tap into a switched 12 volt power source. Fortunately, if you're reading this, that part has been done already.
Using the above pic, you can see that I have removed all the fuses on the Right side, driver side of the vehicle, of the fuse box. Next, remove the fuse box from it's installation bracket and flip it over.
Looking at the above pic, you'll see that I have taken the bottom of the fuse box off and proceeded to remove the power lead spade from the fuse row I mentioned from the above paragraph. To remove this you need to use something like a paper clip to repress the retainers from the top side of the fuse box, and then pull the spade out from the bottom. Be careful as you don't want to damage it. What you'll see is an orange/red wire going to the center terminal. That is your switched power source. There should be two more open crimpable terminals on that spade as indicated by the arrows in the picture. At this point you can go ahead and connect each power leads to the fuse box. You don't need to use a connector of any type, just strip some cover off the wire, and crimp the wire to the terminal. I soldered mine for added security, do as you wish. Once done, go ahead and put the spade back in, it will lock into place. If it doesn't lock into place, remove it again and bend the small locking tabs outward some. Then put the bottom back on the fuse box and reinstall it in the car.
The grounding wires are the easiest part. Just use the two circle connectors, crimp them to the wires, and ground them at any point on the car. I grounded mine at the radiator support frame straight in front of the fuse box.
That's it. Now reconnect the battery, and before driving off, take a lighted probe and ensure that power is indeed getting to the new O2 wiring harness before and after the fuse. If you have a scanner, you can easily tell that they're getting power because they'll start reacting faster and your car will hit closed loop MUCH faster. Enjoy!!