I was stuck in 19 inches of snow and as I was attempting to get my car out my engine light came on, ran a diagnostic and the code P0171, DTC-01 and 02 displayed. After reading these codes do you think I can make these repairs myself if you instruct me on what to do? I’m also a mechanic but have never come across this problem. Thanks, and have a beautiful day! Gary
I would try clearing the codes and driving it to make sure it isn’t just a fluke. If it comes back on, you may meed to dig a little deeper into this issue. Toyota Tech’s say that 99% of the time it is cause from a bad MAF – Sensor.
P0171 Toyota – Air/Fuel Mixture System Lean Bank 1
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
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.)
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).
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