ML 430 (163.172) V8-4.3L (113.942) (2000)
Beneath vehicle, in left exhaust system near engine.
O2S 1 (Before TWC), Right - G3/4
Beneath vehicle, to right of transmission, on exhaust pipe.
O2S 2 (After TWC), Left - G3/5
Beneath vehicle, to left of rear of transmission, on exhaust pipe.
O2S 2 (After TWC), Right - G3/6