2005 c230 kompressor 41k miles

code reads po171 bank 1

since their are 2 upstream o2 sensors before the cat.

how do i know which sensor if their are 2?

i tried getting this fixed but the mechanic said my bosch exact fit 5 wire o2 sensor might fail in a week. changed it anyway.
4 days later cel came back on with same code.

 

If you go to autozone or oreilys and have them read the code, it'll usually tell you which position or o2 sensor it is. It'll say 1 or 2 and usually 1 is the closest sensor to the engine.

 

There have been a few exhaust changes on the M271 but there should only be one O2 sensor before Cat - 130 in this diagram - Please only use genuine Bosch heated replacement - Do not use universal sensors even if they are Bosch.

 

i went to auto zone and it only says bank 1

 

Well there aren't two banks since it is an I4. I took what he said to mean that if it says Bank 1 it is closest to the engine and Bank 2 to mean it is furthest way. Not sure if that's accurate but that's how I took it.

 

L4 has only Bank 1

 

how many o2 senors are on my car?

 

Looks like 2.

 

2 - One pre cat - one post cat.

 

would spraying penatrating oil onto an o2 sensor cause the sensor to go bad?

 

No - Allowing the car to ingest a spray containing silicone would & leaded fuel would but it would take about 20K miles.