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EC-224 < COMPONENT DIAGNOSIS > [QR25DE] P0171 FUEL INJECTION SYSTEM FUNCTION P0171 FUEL INJECTION SYSTEM FUNCTION DTC Logic INFOID:0000000004211461 DTC DETECTION 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 A/F sensors 1. The ECM calcu- lates 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). DTC CONFIRMATION PROCEDURE 1. PRECONDITIONING If DTC Confirmation Procedure has been previously conducted, always perform the following before conduct- ing the next test. 1. Turn ignition switch OFF and wait at least 10 seconds. 2. Turn ignition switch ON. 3. Turn ignition switch OFF and wait at least 10 seconds. >> GO TO 2. 2. PERFORM DTC CONFIRMATION PROCEDURE-II 1. Clear the mixture ratio self-learning value. Refer to EC-18, "MIXTURE RATIO SELF-LEARNING VALUE CLEAR : Special Repair Requirement" . 2. Activate “INSPECTION MODE 1” ( ) to start engine, and let engine idle for at least 5 minutes. 3. Check 1st trip DTC. YES >> Go to NO >> GO TO 3. 3. PERFORM DTC CONFIRMATION PROCEDURE-III 1. Turn ignition switch OFF and wait at least 10 seconds. 2. Turn ignition switch ON (READY). 3. Maintain the following conditions for at least 10 consecutive minutes. Hold the accelerator pedal as steady as possible. CAUTION: Always drive vehicle at a safe speed. 4. Check 1st trip DTC. YES >> Go to Sensor Input signal to ECM ECM function Actuator A/F sensor 1 Density of oxygen in exhaust gas Fuel injection control Fuel injector DTC No. Trouble diagnosis name DTC detecting condition Possible cause P0171 Fuel injection system too • Fuel injection system does not operate properly. large. (The mixture ratio is too lean.) • Intake air leaks VECL SPEED SE 80 - 120 km/h (50 mph - 75 mph) |