Pre cat oxygen sensor. Located before the catalytic converter. Select O2 sensor location from the menu. Made by Uro-Vemo. Part# 11 78 7 558 055 Pre cat in front manifold.Cyl 1-3 (1400mm length) Part# 11 78 7 558 073 Pre cat in rear manifold. Cyl 4-6 (910mm length) Cross Reference: 11787558055 11787558073 17098 17099 0-258-017-0999
