This will show you how to change your front o2 sensors to run off your rear o2 sensor harness. No more extensions, no more corvette sensors, you use your stock wiring harness, and stock length o2s!
When I did this mod originally, the car was on jacks and getting long tubes installed. If you are INSTALLING the long tubes, enjoy using your stock o2s into the stock harness. If you don't know which connector is front or rear, it's the ONLY ones that fit, and has some slight slack in the wire.
If you already have extensions, then you know you have to take them out, and re-connect your o2s onto the rears now.
If you have the Corvette o2s, you might want to wait on this mod until you need new sensors.
Tools you will need:
7mm socket (1/4” or 3/8” drive is fine)
10mm wrench (or whatever size your negative battery cable is)
small flat-tip screwdriver (not jewelers though)
1. Disconnect the battery. (make sure you know your radio code, sound system settings etc.)
2. Loosen the top connector on the PCM with the 7mm socket. It might seem like forever, but just keep going until you can lift the connector off.
3. Lift the connector off, and move it into a good position with plenty of slack in the wires.
4. Remove the gray plastic cover, pushing in on the four tabs. (on the ends)
5. Use the screwdriver to assist you in pushing in the white tabs off the connector. This will give you some more room to play with.
6. Push in the white tabs under the blue cover (the one that ends in wire 40 and 80). It pops right off.
7. Remove the wire by LIGHTLY lifting up on the plastic retainer, sliding the wire FORWARD further into the connector, and then push the wire BACKWARDS (put your finger on the metal end, and give a slight but firm tug on the wire (as close to the metal connector on the WIRE side).
8. Make sure you know what wire you just pulled out. If it was the “Bank 1, Sensor 1 LOW” wire, then this will go into “Bank 1, Sensor 2 LOW” wire slot.
9. The 8 wires you will swap are all colored, a separate color for each oxygen sensor. Pull solid tan wire out, mark it with tape, then pull second tan wire out, insert taped tan wire into un-taped wire's spot.
10. Repeat for all 8 wires. Pin out is as follows: TAN 25+26, TAN-WHITE 28+29, PURPLE 65+66, PURPLE-WHITE 68+69. All 8 wires are next to each other. Tans on top row, purples on bottom row. After pulling out a wire, when re-inserting it, make sure the plastic retaining tab catches the wire and that the metal end is flush with the other wires.
11. To re-assemble, pop the blue cover back on (make sure the "tabbed" side matches the orientation of the other blue cover.
Right is "tabbed side"
12. Snap the connector assembly back into the aluminum housing, ensuring all the white tabs fully snap into place, and everything is flush.
13. Re-install the gray cover (the wires might be a pain to tuck in, but you'll get it). Note the left wires (o2 wires) go above the connector, and the right wires go through the gray cover.
14. Tuck wires under cowl, press on connector to connect the wires back onto the PCM. Make sure it is seated evenly. Torque bolt to the specs on the cover, OR torque until it stops with hand pressure on ratchet, then go 1/8-1/4 turn further.
15. Re-connect battery, start-up, and ENJOY!