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 air fuel ratio (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 lights up the MIL (2 trip detection logic).

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

DTC	CONSULT screen terms (Trouble diagnosis content)	DTC detection condition
P0171	FUEL SYS-LEAN-B1 (System Too Lean Bank 1)	1	Diagnosis condition	-
			Signal (terminal)	-
			Threshold	Fuel injection system does not operate properly.
			Diagnosis delay time	-
		2	Diagnosis condition	-
			Signal (terminal)	-
			Threshold	The amount of mixture ratio compensation is too large. (The mixture ratio is too lean.)
			Diagnosis delay time	-