P0171 TOYOTA - Air/Fuel Mixture System Lean Bank 1
Repair Importance Level:
Repair Difficulty Level:
Possible causes
- Intake air leaks
- Faulty front heated oxygen sensor
- Ignition misfiring
- Faulty fuel injectors
- Exhaust gas leaks
- Incorrect fuel pressure
- Lack of fuel
- Faulty Mass Air Flow (MAF) sensor
- Incorrect Positive Crankcase Ventilation (PCV) hose connection
Tech notes
If the P0171 is combined with the P0174 code, it's very likely that the problem is caused by an intake leak. If there are no intake leaks, the next step is to replace the air filter and clean the air flow meter. If the problem persists the front oxygen (O2) sensor may need to be replaced.
There is a factory service bulletin for the following Toyota models:
2005–2007 Toyota Avalon
2007–2008 Toyota Camry
2005-2007 Toyota Avalon, 2007-2008 Toyota Camry Service Bulletin OBDII Code P0171
2005-2006 Toyota Corolla
2005-2006 Toyota Corolla Service Bulletin OBDII Code P0171
User Submitted Video
There is a factory service bulletin for the following Toyota models:
2005–2007 Toyota Avalon
2007–2008 Toyota Camry
2005-2007 Toyota Avalon, 2007-2008 Toyota Camry Service Bulletin OBDII Code P0171
2005-2006 Toyota Corolla
2005-2006 Toyota Corolla Service Bulletin OBDII Code P0171
User Submitted Video
When is the code detected?
- Fuel injection system does not operate properly.
- The amount of mixture ratio compensation is too small. (The mixture ratio is too lean.)
- The amount of mixture ratio compensation is too small. (The mixture ratio is too lean.)
Possible symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
- Excessive Fuel Consumption
P0171 TOYOTA Description
In case the amount of the compensation value is extremely large (The actual mixture ratio is too lean.), the ECM judges the condition as the fuel injection system malfunction and light up the MIL (2 trip detection logic).
P0171 TOYOTA Information for specific Toyota models
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P0171 TOYOTA Comments
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