If you need to replace the wiring to your oxygen sensor from your ECU then this is the kit you need. Do you have the following symptoms: Starts and runs great first thing in the morning. Then as you drive it, it starts to run poorly, bog down, have no acceleration, and even blow black smoke? Then you turn it off and back on again and it runs great again for a short time and then starts doing it again? You are describing what I like to call Oxygen Sensor Syndrome and it can happen when either your oxygen sensor is bad or if the wiring from the sensor to the computer is bad. I have found more and more, it is the second thing. You could replace your entire engine wiring harness (we have those) or you could just repair the oxygen sensor harness. That is what this repair harness is. How to replace it? You will have to open up your ECU plug which is pretty easy, and get the old pin out, then install this new wire from the ECU plug (under the rear seat) to the area near the coil. Just tie wrap as you go. You can leave the old wire in the harness, no need to pull it out, it will just be no longer used. I would cut the ends off to avoid confusion in the future. On the 86-91 2.1l Vanagon you are looking at Pin number 2 in your harness. Once you remove the ECU plug cover you will see the numbers on the white plastic of the back side of the plug. Pin 2 is the one you want to remove and replace with this new harness. Quick temporary fix: If you are in a pinch on a trip, you can actually cut the wire at pin 2, leave about an inch of the old wire, tape it off with electrical tape, and then continue on your trip. The computer will use a default reading for the oxygen sensor and the van will run fine the rest of your trip. Then once you get where you are going you can order this kit to fix it correctly or an entirely new engine harness (take your pick).