Q: OBD-II codes P2195 and P0171 appear

P2195 and P0171 occur when the engine is running too rich (too much fuel relative to air charge) and the engine feedback system is unable to compensate. The "how can you fix this" depends on which component(s) in the system are malfunctioning and because there are multiple components involved, you have to go through a step by step exam. You’ll want to check for excessive (out of spec) fuel pressure which, if it exists, could be due to a faulty fuel pressure regulator.

Other possibilities are that the fuel injectors are sticking, leaking, or clogged. Leaks in the intake or intake hose as well as leaks between the mass air flow sensor and the throttle body, loose intake manifold bolts and other vacuum leaks can account for these codes. Finally, the oxygen sensor itself could be damaged (typically contaminated), by say an internal engine oil leak through the valve stem oil seals or piston rings, causing the sensor to falsely report a lean operating condition and "fooling" the engine into adding fuel. A technician from YourMechanic can evaluate all these possibilities for you and pinpoint the reason why the codes are setting.