OBD-II Trouble Code Description for P0171 Subaru

System Too Lean

What does this mean?

OBD2 Code P0171 Subaru definition:
Basically this means that an oxygen sensor in bank 1 detected a lean condition (too much oxygen in the exhaust). On V6/V8/V10 engines, Bank 1 is the side of the engine that has cylinder #1. Note: This DTC is very similar to P0174 Subaru, and in fact your vehicle may show both codes at the same time.

Symptoms

Possible sumptoms of OBD code P0171 Subaru
You will more than likely not notice any drivability problems, although there may be symptoms such as a lack of power, detonation (spark knock), and/or a hesitation/surge on acceleration.

Causes

Possible causes of OBD code P0171 Subaru
A code P0171 Subaru may mean that one or more of the following has happened: ?The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of “oiled” air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry. ?There could be a vacuum leak downstream of the MAF sensor.

Possible Solutions

Possible solutions include: ?In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it’s location if you need help. I find it’s best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it’s dry before reinstalling ?Inspect all vacuum and PCV hoses, replace if necessary ?Check for a dirty fuel filter and proper fuel pressure