Check-light

Tiny
MAPLECREST
  • MEMBER
  • 2000 TOYOTA TACOMA
  • 4WD
  • MANUAL
  • 88,025 MILES
MY TOYOTA TRUCK CHECK LIGHT CODE IS PO171. IS THAT A SEVERE REPAIR PROBLEM?
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Thursday, December 23rd, 2010 AT 2:09 AM

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Tiny
OBXAUTOMEDIC
  • EXPERT
Hello,

Here is the Code Def.

P0171 System too Lean (Bank 1)

Here is diagnostic.

Section 1 - Lean mixture code for bank 1 or bank 2 (V6, V8, V10 and V12 engine only)

Step 1: Use a simple scanner tool to retrieve trouble codes and check if they relate to a specific cylinder, like an ignition coil or fuel injector failure code and repair as needed. Once the repairs have been made clear the trouble codes and recheck system. If a trouble code is present but does not pertain to the immediate problem like an EVAP failure code it must be checked. The reason we repair non-related codes is if the component is vacuum driven, it might be leaking causing a lean mixture code. If no trouble codes (besides the lean mixture codes) are present proceed to the next step.

Step 2: If your engine is running rough with no additional trouble codes it will produce a lean mixture DTC (diagnostic trouble code). You must determine what is causing the engine misfire. Please follow this link to troubleshoot the problem, engine misfires If your engine is running ok proceed to the next step.

Step 3: The exhaust system is used to transfer exhaust gases to the rear of the vehicle. If an exhaust leak is present before the oxygen sensors it can cause the sensor to produce a false reading. You might say a leak will not affect the reading because the exhaust is simply leaking out. The problem is that theory is not exactly true. Engine exhaust is produced in pulses as the cylinder's fire. When the exhaust valve opens pressure is created in the exhaust system while the spent mixture exits the combustion chamber. But then a vacuum condition in the exhaust is created after the exhaust valve closes. This vacuum condition can draw raw oxygen from outside of the system and cause a false reading. To inspect for an exhaust leak, start with a cold engine. Then have a helper start the engine and hold the idle at about 1500 rpm. Next, try to listen for any exhaust noises coming from any part of the exhaust system including the exhaust manifold and head pipe. Also look for black soot at any point in the system as this can be the source of an exhaust leak. If an exhaust leak is detected repair leak and recheck system. If no exhaust leak is detected continue to the next step.

Step 4: The oxygen (O2) sensor is designed to deliver feedback voltage to the PCM. If the sensing element fails it will not deliver the proper feedback information causing a lean mixture code. To test the oxygen sensor follow this link - How to test an oxygen sensor.

And to answer the 2nd part of your question - It isn't a servere repair but you should get it fixed as soon as you can.
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Thursday, December 23rd, 2010 AT 3:12 AM

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