I recently bought a 2012 Subaru outback and the check engine light has recently come on and off a couple of times, it is currently on. The code I am getting is P2096, a lean fuel to air mixture downstream of the cat converter. I am not noticing any performance issues, and was hoping to get some feedback from others that have experienced this. I’m guessing it is an emission control sensor? What should I check before taking it into a mechanic to try to change the oxygen sensors or the mass airflow sensors. Any quick remedies that might work?
Chris.Herman
This code can be caused by a few different things. Vacuum leak, dirty MAF sensor, incorrect ECT function or temperature control issue, bad rear O2 sensor, bad front AF sensor, poor fuel delivery or a weak battery and grounds.
Data will give a direction. The short term fuel trim is apparently high, in the positive range, while the car is idling or cruising. The rear O2 sensor is giving low voltage feedback which means a high amount of oxygen and this relates to a lean combustion occurring. Whether it is really running lean or not has to be determined by looking at data and checking sensor function.
How many miles on the car? Is it up to par on maintenance?
Most times it is either a lazy rear O2 or the front AF sensor. This is as long as the battery is putting out sufficient amperes and the grounding is good. I've also run in to instances where someone changed an air filter and the clamps didn't get tightened which creates a vacuum leak since air gets in the system after the MAF. This unmetered air means the computer is adding fuel on top of what it is programmed to run based on MAF feedback.
Data will give a direction. The short term fuel trim is apparently high, in the positive range, while the car is idling or cruising. The rear O2 sensor is giving low voltage feedback which means a high amount of oxygen and this relates to a lean combustion occurring. Whether it is really running lean or not has to be determined by looking at data and checking sensor function.
How many miles on the car? Is it up to par on maintenance?
Most times it is either a lazy rear O2 or the front AF sensor. This is as long as the battery is putting out sufficient amperes and the grounding is good. I've also run in to instances where someone changed an air filter and the clamps didn't get tightened which creates a vacuum leak since air gets in the system after the MAF. This unmetered air means the computer is adding fuel on top of what it is programmed to run based on MAF feedback.
connect scan tool and observe the following
what are your grams per second airflow past the MAF? should be close to engine displacement when fully warmed up
are the rear o2 sensor(s) holding steady or are they following the primary A/F sensors
what are your grams per second airflow past the MAF? should be close to engine displacement when fully warmed up
are the rear o2 sensor(s) holding steady or are they following the primary A/F sensors
- Low fuel pressure
- Misfire condition
- Large vacuum leak
- Air leak near sensor
- Plugged catalytic converter
- Lean air/fuel ratio
- Faulty front O2 sensor
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