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Engine trouble code P0171 indicates that the air-fuel mixture is too lean. You can often resolve the issue yourself with the help of the vehicle manual.
These are the causes of engine trouble code P0171
- If the sensor wiring is defective, damaged, or faulty, you will receive this error code.
- A leak in the air intake is also possible. Check the vacuum hoses or the charge air hose. Also check the crankcase breather valve.
- Check the fuel pressure. In the case of a lean mixture, low or excessively low pressure can be a problem. The cause may be a defective fuel pump, filters, or pressure regulators.
- Inspect the EVAP purge valve for defects or damage. EVAP stands for “Evaporative Emission.”
- Check the vehicle’s oxygen sensor. If necessary, replace the sensor.
- Sometimes the exhaust gas recirculation (EGR) system is faulty. In this case, the EGR valve is defective. Normally, the system reduces NOx emissions. However, high stress on the system, especially with high mileage on your vehicle, can lead to problems.
- The air pressure sensor may be defective or malfunctioning. In this case, you should check the mass air flow sensor.
- Check for possible leaks in your vehicle’s exhaust system, particularly the oxygen sensor.
- In some cases, the P0171 engine fault code may be caused by a defect in the engine control system, specifically the engine control unit.
This is how engine trouble code P0171 appears
As with other engine trouble codes, the engine check light comes on by default.
- You notice changes in engine speed, particularly when idling or accelerating. The speed fluctuates, is too low, or too high.
- The usual engine power is not available, and the engine is weaker than usual.
- Similar to engine fault code P0300, occasional misfires caused by the mixture being too lean may be audible.
- Starting difficulties may also occur. The engine may also stall while driving.
