P0171 System Too Lean (Bank 1)

[Donkey]

Thats how they both work (MAF & MAP) in closed loop. Openloop does not use O2 sensor feedback. You might want to think about taking this car to a professional.............

[BrandonPaquette]

So map is closed loop?

[Donkey]

So map is closed loop?

No..........both MAF and MAP use both closed and openloop fueling. At idle and part throttle you are in closed loop for best fuel economy and emissions. At W.O.T. you go into Openloop fueling. Difference with the Subaru is the ECU now thinks your MAF is broken and now is using the "limp" mapping for fueling and timing. You are technically in a lower state of tune when defauled to the MAP sensor. Google might help explain more about OP/CL fueling.........