P0171 Toyota

P0171 Toyota Fuel SystemLean Bank 1

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P0171 Toyota Fuel System  
Lean Bank 1

P0171 Lean is a very common fault code on Toyota’s.  In this Detailed article I am going to be discussing the 1.8, 2.4 4 cylinder engines in the Toyota Corolla, Camry, Rav4 and Matrix along with the V6 3.5-liter engine used in the Camry, Avalon, Solara, and Sienna van.  The last vehicle on this page is the Highlander.  I did not cover the Toyota Tacoma or Tundra.  However, keep in mind, the theory and operation is still the same when it comes to a lean condition on the V8 engine and all other internal combustion engines with this similar Toyota fuel system. First is a brief overview of this code.  A P0171 Diagnostic trouble code indicates a lean condition on bank one.   Bank 1 is the side of the engine or “bank” that the number 1 cylinder is on.   Bank 2 is simply the other bank.   If it is a 4 cylinder engine, there is only one bank.  Below is a list of the more common Toyota engines you will see.  

(Note: Below I make Video about P0171 Toyota Fuel System Lean Bank 1 Problem Solution You Cn Watch the Video of This Fault Code)

What are the 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

There is a factory service bulletin for the following Toyota models:
2005–2007 Toyota Avalon
2007–2008 Toyota Camry
2005-2006 Toyota Corolla

When is the code detected?

1. Fuel injection system does not operate properly. 
2. The amount of mixture ratio compensation is too small. (The mixture ratio is too lean.)

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Possible symptoms

• Engine Light ON (or Service Engine Soon Warning Light)
• Excessive Fuel Consumption

P0171 Toyota Description

With the Air/Fuel Mixture Ratio Self-Learning Control, the actual mixture ratio can be brought closely to the theoretical mixture ratio based on the mixture ratio feedback signal from the heated oxygen sensors 1. The Engine Control Module (ECM) calculates the necessary compensation to correct the offset between the actual and the theoretical ratios.

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)

According to this TSB, the fix is to replace both front Air-fuel Ratio sensors and recalibrate or update the PCM.  The newly updated part numbers for the air-fuel ratio for bank 1 is 89467–48060 and for bank 2 is 89467–48050.

While these last two TSB’s do not specifically talk about the P0171 lean code, if the air-fuel ratio sensor goes bad, it can definitely cause a lean condition.

Check Out More Toyota Fault Code Problem Solution

If You Did not understand you can Watch Detailed video About P0171 Toyota Fuel System  Lean Bank 1 Problem

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