i have a 96 ek, modified dx harness with a obd2-1 conversion clip running a p28, which only looks for 1 o2 sensor. i've been experiencing the "closed loop" hesitation/missing problem, and when i got to my car after 3 months of storage i found out that the problem is coming from the o2 sensor, the problem is there regardless if the o2 sensor's plugged in or not. now i can only think of 2 possible explanations: 1: the o2 sensor is bad 2: the wiring is messed up: secondary wired to primary, primary to secondary. p28 looks for the primary and its not there. my questions: -i'd like to test my o2 sensor, can anyone enlighten me on how to do so? -is my o2 sensor supposed to have 4 wires? -is there anyway to wire the o2 sensor to the ecu without having to have it plugged in to the wiring harness? thanks guys.