The P0171 code means that the engine control unit (ECU) has detected that the air-fuel mixture in the engine is too lean. This means that there is not enough fuel being mixed with the air, which can cause the engine to run rough, stall, and/or lose power.
There are a number of things that can cause the P0171 code to be set, including:
* A vacuum leak: A vacuum leak can allow unmetered air to enter the engine, which can cause the air-fuel mixture to become lean.
* A faulty oxygen sensor: The oxygen sensor is used to measure the amount of oxygen in the exhaust gas. If the oxygen sensor is faulty, it can send an incorrect signal to the ECU, which can cause the air-fuel mixture to become lean.
* A faulty fuel injector: A faulty fuel injector can fail to deliver enough fuel to the engine, which can cause the air-fuel mixture to become lean.
* A faulty mass air flow sensor: The mass air flow sensor is used to measure the amount of air entering the engine. If the mass air flow sensor is faulty, it can send an incorrect signal to the ECU, which can cause the air-fuel mixture to become lean.
If you see the P0171 code on your Toyota Corolla, it is important to have the code diagnosed and repaired as soon as possible. Driving with a lean air-fuel mixture can damage the engine and/or catalytic converter.
