I have a 2009 Saab 9-7X with engine code P0171

Question

Just had the car serviced new air filter put in the next morning engine light on checked code and was p0171

Answer 1

P0171 Fuel trim lean

What did the service include, when there is a lean code condition the number 1 cause is vacuum leaks, a hose getting disconnected it can be something very simple or major, but if this was just serviced something like a vacuum hose just got knocked off. Here is a Toyota with a air filter change, the next day it had a EVAP code, what happen during the airfilter change just to access the airfilter one of the purge line got disconnected and went unnoticed until the CK ENG LT appeared.