Excessive nitrogen oxides (NOx) emission

Perform troubleshooting referring to the following points when ECM has detected no DTC and no abnormality has been found in Visual Inspection:K14C and Engine Basic Inspection:K14C.

Condition	Possible Cause	Action
Excessive nitrogen oxides (NOx) emission	Improper ignition timing	Ignition Timing Inspection:K14C
	Lead contamination of TWC	Check for absence of filler neck restrictor.
	Fuel pressure out of specification	Fuel Low-Pressure Basic Check:K14C and Fuel High-Pressure Basic Check:K14C
	Faulty closed loop system (A/F feedback compensation) (Poor performance of ECT sensor, MAP sensor or MAF sensor)	ECT Sensor Inspection:K14C, MAP Sensor Inspection:K14C or MAF Sensor with IAT Sensor-1 Inspection:K14C
	Faulty electric throttle body assembly	Electric Throttle Body Assembly On-Vehicle Inspection:K14C
	Faulty APP sensor	APP Sensor Inspection:K14C
	Faulty fuel injector	Fuel Injector Circuit Check:K14C or Fuel Injector Inspection:K14C
	Faulty ECM	Inspection of ECM and Its Circuits:K14C
	VVT system out of order	•VVT actuator: Camshaft and VVT Actuator Inspection:K14C •Valve timing: Timing Chain and Chain Tensioner Inspection:K14C •OCV oil circuit: Timing Chain Cover Inspection:K14C