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Discussion Starter #1
My friends nitrous fed 01 GT ran these codes from an OBD II Diagnostic scanner:

P1151 - Lack of HO2S21 Switch - Sensor Indicates Lean

P0174 - System too lean (Bank 2)

Can someone help us out.. I'm thinking bad O2 sensor

Thanks in Advance!
 

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I'm thinking your right... This is pointing to a drivers side front O2 sensor. Have you done any exhaust work lately? Are you sure you dont have any exhaust leaks?

[edit] if the answer is yes to the above two questions swap the front O2 sensors and see if it follows the O2 sensor, IE now you will get passenger side codes (bank 1)
 

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Discussion Starter #3
re

There has not been any exhaust work.. but there is a slight exhaust leak at the manifold I believe.. Could a simple exhaust leak flag the check engine like that?

THX again for your help
 

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Yes an exhaust leak can throw a code. I would fix that first. If it doesnt clear up then swap the O2's side to side and see if it follows it.
 
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