I have an 06 endeavor that could not pass emissions testing in Fort Worth Texas. My cousin took it to a shop and they did a cut-and-paste job on the under hood wiring. It looks as if they may have wired in a different O2 sensor on the number 1 and number 2 Upstream. They have four red wires spliced into the factory wiring going to the new O2 sensor. I'm wondering what the four colored Factory wires go to? how do they correspond to aftermarket O2 sensors? I am getting Upstream O2 sensor codes now on the OBD2 scanner. Any help would be appreciated

 

I ran a check on both upstream o2 sensors. Bank 2 has continuity at the heating element but the resistance. Is much higher than bank 1. I believe both to be new generic 02 sensors. Whomever installed them broke the factory plug by trying to force the generic plug into it. Then they rewired the sensor into the factory sensor plug so it would fit. The bank 2 sensor was crammed into the factory plug but I doubt it was making connection. I pulled them apart and filed the tabs off the generic sensor so it would fit. Still getting no o2 reading upstream reading on ob2 scan. I'm thinking they bought a pair of sensors and one was for downstream since one had a much higher resistance for the heating element. Maybe should replace withcorrect and see what happens.???