WARNING: This page is about a different car, the 2008 Mitsubishi Lancer. However, it is still accessible from the selected car via links, so may be relevant.
Tighten the heated oxygen sensor to the specified torque by using special tool MB991953.
Tightening torque: 44 ± 5 N.m (33 ± 3 ft-lb)
Fig 1: Tightening Heated Oxygen Sensor And Special Tool MB991953