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Toyota Corolla Code P0171 Check Engine light

Code P0171 on Toyota Corolla Q: What could cause the code P0171 on 2002 Toyota Corolla? A: The code P0171 reads "System Too Lean (Bank 1)". This means that the air-fuel mixture coming in to the engine is too lean, or there is too much air and too little fuel. This could be caused by a number of reasons, such as bad airflow sensor, vacuum leaks, low fuel pressure, clogged fuel injectors, etc. To know exactly what caused the problem, your mechanic can do a few tests.
From my experience, the airflow sensor problems are fairly common; sometimes the sensor just gets dirty and gives false air flow readings causing lean condition. Again, your mechanic can test it.
If the airflow sensor is causing the lean condition, it will need to be replaced. If the sensor is just dirty, your mechanic may suggest to clean it (cleaning the airflow sensor is very delicate procedure) as a temporary solution - sometimes this could work.

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Im getting P0171 code- lean .


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what does code system to lean bank 1 mean on my 2000 lexus rx300


It could be caused by many things, but generally it means that your engine is running too lean - usually indicating a vacuum leak. It could also be that the O2 sensor is bad and giving a false reading.

Apr 10, 2014 | 2000 Lexus RX 300

1 Answer

My 2005 Corolla is exhibiting a P171. I have sprayed the MAF element with throttle body cleaner and the check light stays on, even after a long journey. Is there a correct way to spray the MAF?


If you have reset the check light and it comes back on and stays on, then it may a problem other than a dirty MAF. That code (P0171) means "system too lean (bank 1)" It may be that there is an air leak that is causing a lean condition. Look for intake air leaks, vacuum leaks, and exhaust leaks.

Jan 24, 2011 | 2005 Toyota Corolla

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What is engine code P0171 for 2005 Toyota corolla?


What does that mean? 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, and in fact your vehicle may show both codes at the same time.
Symptoms 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 A code P0171 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.

Dec 08, 2010 | 2005 Toyota Corolla

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