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EC-172 < COMPONENT DIAGNOSIS > [VQ40DE] P0138, P0158 HO2S2 P0138, P0158 HO2S2 Component Description INFOID:0000000005257155 The heated oxygen sensor 2, after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. Even if switching characteristics of the air fuel ratio (A/F) sensor 1 are shifted, the air-fuel ratio is controlled to stoichiometric, by the sig- nal from the heated oxygen sensor 2. This sensor is made of ceramic zirconia. The zirconia generates volt- age from approximately 1V in richer conditions to 0V in leaner condi- tions. Under normal conditions the heated oxygen sensor 2 is not used for engine control operation. On Board Diagnosis Logic INFOID:0000000005257156 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 (manifold) causes the longer switching time. MALFUNCTION A To judge the malfunctions of heated oxygen sensor 2, ECM monitors whether the voltage is unusually high during various driving condi- tions such as fuelcut. MALFUNCTION B To judge the malfunctions of heated oxygen sensor 2, ECM monitors whether the minimum voltage of sensor is sufficiently low during var- ious driving conditions such as fuelcut. SEF327R PBIB1848E PBIB2376E DTC No. Trouble diagnosis name DTC detecting condition Possible cause P0138 Heated oxygen sensor 2 cir- A) An excessively high voltage from the • Harness or connectors (The sensor circuit is open or shorted) • Heated oxygen sensor 2 P0158 B) The minimum voltage from the sensor • Harness or connectors (The sensor circuit is open or shorted) • Heated oxygen sensor 2 2010 Pathfinder |