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Home >> Infiniti >> 2005 >> G35 x >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 7 (Engine Control System - Coupe) >> DTC P0171, P0174: Fuel Injection System Function >> On Board Diagnosis Logic
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On Board Diagnosis Logic

WARNING: This page is about a different variant/trim than selected.

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 air fuel ratio (A/F) sensors 1. 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).

AIR FUEL RATIO (A/F) SENSOR 1 SIGNAL AND ECM FUNCTION

Sensor Input signal to ECM ECM function Actuator
Air fuel ratio (A/F) sensor 1 Density of oxygen in exhaust gas (Mixture ratio feedback signal) Fuel injection control Fuel injector
Fig 1: On Board Diagnosis Logic Chart (DTC P0171 & P0174)
G02333503Courtesy of NISSAN MOTOR CO., U.S.A.