Replace up-stream Oxygen sensor in 99 corolla CE 4 cylinder.

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I unscrewed my O2 sensor, and its loose, but there's a bolt hanging from the above exhaust manifold which is blocking its removal. Request your assistance. As a reference; if you go to this link & scroll down; you will see the snaps of O2 sensor. I have the same issue which he is facing. http://www.corolland.com/forums/index.php?/topic/23047-2002-corolla-location-of-pre-cat-oxygen-sensor/ Thanks, Sajith