How do i find bank 1 sensor 1 on a mits montero sport 3.0 l

Bank 1 is the passenger side, so yes, the left side at you stand in front and face the windshield..

https://mitsubishiforum.com/forum/mitsubishi-montero-montero-sport-14/o2-sensor-bank-2-a-30747/

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bank 1 sensor 1 is on the exhaust manifold of the passenger side of your truck

two engines used one facing front of truck and one sideways. Facing front of truck then left bank from front towards back is 135 right bank is 246 firing order is 123456,
so

6
5
4
3
2
1

front of engine

are we talking about o2 sensors ? if so bank 1 is the 1 before the catalic convertor and bank 2 if after the cat .

P0130 - O2 Sensor Circuit Bank 1 Sensor 1
P0135 - O2 Sensor Heater Circuit Bank 1 Sensor 1

Here is a visual aide that will clear up the confusion on where the affected sensor is located.

replace the o2 sensor the one before the cat converter with a quailty sensor like a denso brand o2 sensor

P0151 O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1)
this could be a fluke code I would earse it and see if it comes back before putting the sensor in there not cheap. Bank 2 means witch side of the engine bank 1 is the side that #1 cylinder is on bank 2 is the other side sensor 1 means upstream above the catalytic converter on the engine side sensor 2 is below the catalytic converter

my 1998 Montero Sport has 4

autozone.com "repair info" shows:
2.4L Engine Firing order: 1-3-4-2 Distributor rotation: Counterclockwise

P0154 HO2S-11 (Bank 1 Sensor 1) No Activity Detected
P0174 Fuel System Lean (Bank 2)