What does a OEM fault code P1273 mean on a 2004 Nissan Altima? How can i check

and repair? The P1273 fault code read as follows; AF sensor lean shift detected. The repair manual said that all models 2000 and later had an updated engine management system which could not be checked by the same procedure given for a standard Mass Airflow sensor. A check procedure was not given.The root causes for this fault was #1-Failed AF sensor,# 2- Vacuum leak in engine and #3- Fuel injectoror pressure regulator fault.

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