A long story I will shorten it the best I can. I bought a 2007 Chevy Tahoe 4x4 with 95000 miles on it from my girlfriends dad. It had some issues mostly used in the countryside hunting, fishing, camping, etc. Living in the countryside they did not need to follow emission standards that us city folk do, so when they got the engine code for O2 sensor failure they just ignored it. Cut all wires to be honest, although why they didn't bother explaining that part. Now its mine, runs great, did a lot of minor fixing here and there but need to get the sensors right so it can pass emissions and get her registered. I followed a lot of guides that I can find online, wiring diagrams, etc, but cannot get this correct. I always end up with the codes P0036 and P0056. I got new O2 sensors and errors messages for both sensor 1 have disappeared except for these two that come up for number 2 sensors. Mentioned that they cut the wires for some reason, well they did but not the front ones only the rear (downstream) sensors. Why? I don't know. So i found a pair of male pig tails for the downstream sensors and haven't been able to get the wiring straight. At least that is what I think it is. Checked fuse, its ok. Tested wires to see if there were any breaks and nothing that i can find. The pink wire has the correct voltage. I know the pig tails I found the wire colors weren't perfectly matched but as long as the wiring is correct, A-A, B-B, C-C, D-D, it should be good. They fit the new O2 sensors perfectly. I haven't done a complete installation (using black electrical tape until I am sure that the wiring is correct because I don't have a lot to be cutting off) so I am stuck where I am. And the error has not gone away, P0036 and P0056. I bought Bosch brand O2 Sensors all around and the basic color configuration is two white wires (A-B), one gray (C), and one black (D). So what I am asking is can anyone help me with a wiring diagram for this Tahoe? I have attached a picture of the wires that are coming out of the Tahoe. The first is for Bank 1 and the second for Bank 2, they are slightly different from each other. And I have yet to find any information that references these exact wire colors. Some close but no exact match. Maybe that is my error, assuming too much. If not maybe the whole catalytic converter just needs to be replaced. But there were no error messages pointing in that direction. Thanks for any help.