DTC P0171 FUEL INJECTION SYSTEM FUNCTION (LEAN SIDE) - On Board Diagnosis Logic
EF & EC-7154prose procedureOn Board Diagnosis Logic
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 sensor 1 (front). The 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 lights up the MIL (2 trip detection logic).
Sensor/ECM/Actuator Map
Heated oxygen sensor 1 (front)
Input Signal to ECMDensity of oxygen in exhaust gas (Mixture ratio feedback signal)
ECM functionFuel injection & mixture ratio control
ActuatorInjectors
DTC P0171 Malfunction Detection / Possible Causes
P0171
Malfunction is detected when ...- Fuel injection system does not operate properly.
- The amount of mixture ratio compensation is too large. (The mixture ratio is too lean.)
Check Items (Possible Cause)- Intake air leaks
- Heated oxygen sensor 1 (front)
- Injectors
- Exhaust gas leaks
- Incorrect fuel pressure
- Lack of fuel
- Mass air flow sensor
- EVAP canister purge volume control solenoid valve stuck open