Has anyone changed their rear O2 sensor. The 4-wire harness goes through a small grommet on the underbody. Can the connector be reached through from under the car. The grommet hole seems too small to reach the connector. I did not want to just pull off the grommet to see if the wiring harness was long enough on the other end. It almost appears as if the connector needs to be accessed from under the passenger seat.

 

Following assumes you have a 2004-2008 TSX. It helps to put this info in your signature.

The connector must be released inside the car, grommet pushed out, and connector fed through the opening to underside. Release wire from clips. Use O2 socket or open end wrench to break the O2 sensor loose and remove.

A identical replacement part is recommended over universal 4-wire sensor to avoid the cutting/splicing problem. I just did this on a celica w/ similar O2 sensor arrangement and it was tedious.

good luck