DTC Detection Logic

The heated oxygen sensor 3 has a much longer switching time between rich and lean than the air fuel ratio (A/F) sensor 1. The oxygen storage capacity of the three way catalyst (manifold) causes the longer switching time. To judge the malfunctions of heated oxygen sensor 3, ECM monitors whether the voltage is unusually high during the various driving condition such as fuel-cut.

Fig 1: Heated Oxygen Sensor 2 Voltage Signal Waveform

Courtesy of NISSAN NORTH AMERICA, INC.

DTC DETECTION LOGIC

DTC No.	Trouble diagnosis name	DTC detecting condition	Possible cause
P0146	Heated oxygen sensor 3 circuit no activity detected	An excessively high voltage from the sensor is sent to ECM.	Harness or connectors (The sensor circuit is open or shorted) Heated oxygen sensor 3