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 A/F sensor 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 illuminates the MIL (2 trip detection logic).

Sensor	Input signal to ECM	ECM function	Actuator
A/F sensor 1	Density of oxygen in exhaust gas (Mixture ratio feedback signal)	Fuel injection control	Fuel injector

Fuel injection system does not operate properly.
The amount of mixture ratio compensation is too large. (The mixture ratio is too lean.)

DTC	CONSULT screen terms (Trouble diagnosis content)	DTC detection condition
P0171	FUEL SYS-LEAN-B1 (System too lean bank 1)	1	Diagnosis condition	Start engine and let it idle Start engine and drive the vehicle
			Signal (terminal)	-
			Threshold	Fuel injection system does not operate properly.
			Diagnosis delay time	-
		2	Diagnosis condition	Start engine and let it idle Start engine and drive the vehicle
			Signal (terminal)	-
			Threshold	The amount of mixture ratio compensation is too large. (The mixture ratio is too lean.)
			Diagnosis delay time	-
P0174	FUEL SYS-LEAN-B2 (System too lean bank 2)	1	Diagnosis condition	Start engine and let it idle Start engine and drive the vehicle
			Signal (terminal)	-
			Threshold	Fuel injection system does not operate properly.
			Diagnosis delay time	-
		2	Diagnosis condition	Start engine and let it idle Start engine and drive the vehicle
			Signal (terminal)	-
			Threshold	The amount of mixture ratio compensation is too large. (The mixture ratio is too lean.)
			Diagnosis delay time	-