Hello, I have a 1997 Honda Civic Coupe with a d16y7. I'm trying to figure out which O2 sensor is which. One is upstream and one is Downstream. One of the leads is longer than the other. Does anyone know which is which? My car has the cat on the manifold if that matters... Also, one of the lead connections is attached to the block with a bracket.

 

is a YouTube video of a lady changing her upstream O2 sensor.

The upstream O2 sensor sticks out of the hole in the top middle of the exhaust manifold head shield.
The downstream O2 sensor is easily accessed from underneath the car.

Here are the part numbers:
Denso 234-4099 upstream OE style
Denso 234-4065 downstream OE style

Get the OE style, not the Universal style. The wiring is easier to deal with.

RockAuto.com has good prices.

 

I'm trying to figure out which connector on the harness is which. The connectors are the same on each sensor. It's hard to tell in this video.

 

This photo shows a 1996 Civic DX (w/ a stock D16Y7 engine). The front of the car is at the bottom of the photo. The upstream O2 sensor is circled in red. The downstream O2 sensor is circled in green. The harness connector for the downstream sensor is about 6 inches lower than the upstream one and closer to the catalytic converter.

 

Yay! You're awesome!