DTC Detection Logic

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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 various driving conditions such as fuel cut.

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DTC No.

Trouble diagnosis name

(Trouble diagnosis content)

DTC detecting condition

Possible cause

P0139

HO2S2 (B1)

[Heated oxygen sensor 2 (bank 1) circuit slow response]

The switching time between rich and lean of a heated oxygen sensor 2 signal delays more than the specified time computed by ECM.

Harness or connectors
(Heated oxygen sensor 2 circuit is open or shorted)
Heated oxygen sensor 2
Fuel system
EVAP system
Intake air system