I was recently given a 91 Civic Si Chassis, with a D15b2 Engine. The guy who gave it to me told me it needed the upstream 02 sensor plugged in. I've been looking all through the engine bay and I cannot for the life of me find where it should be plugged into. The only wires anywhere near it plug into the transmission (which also is quite concerning having un-used wires) If anybody could help me this is my first Honda and I need it to be plugged in the pass emissions. Also the reverse lights do not illuminate when I put it in reverse, the lights are there they just aren't getting power somehow. Could definitely use some help here.

 

Check the left side of the exhaust manifold.