I swapped the tranny in my 03 300m. The trans I put in had the wiring harness on it so I just swapped it with harness on it. I only had to plug in the 2 big connections on top of the tranny and the O2 sensors. Everything works great but the engine light is on. I checked the codes and both downstream O2 senssors and trans sensors show up, everything thats included off that "new" harness. I tried clearing them but they came right back. Anyone have any ideas how I can get rid of them?