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Home >> Infiniti >> 2008 >> EX35 Base, RWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - DTCS P0137 To P0448 >> P0139, P0159 Ho2S2 >> DTC Logic >> DTC Detection Logic
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DTC Detection Logic

The heated oxygen sensor 2 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 1 causes the longer switching time. To judge the malfunctions of heated oxygen sensor 2, ECM monitors whether the switching response of the sensor's voltage is faster than specified during the various driving condition such as fuel-cut.

Fig 1: Heated Oxygen Sensor Voltage Waveform
G04875089Courtesy of NISSAN MOTOR CO., U.S.A.
DTC DETECTING CONDITION AND POSSIBLE CAUSE REFERENCE

DTC No. Trouble diagnosis name DTC detecting condition Possible cause
P0139 Heated oxygen sensor 2 (bank 1) circuit slow response It takes more time for the sensor to respond between rich and lean than the specified time.
  • Harness or connectors

    (The sensor circuit is open or shorted) Heated oxygen sensor 2

  • Fuel pressure
  • Fuel injector
  • Intake air leaks
P0159 Heated oxygen sensor 2 (bank 2) circuit slow response