DTC : P0138 (2021): General Description
The rear secondary heated oxygen sensor (secondary HO2S (bank 1, sensor 2)) detects the oxygen content in the exhaust gas downstream of the rear warm up three way catalytic converter (WU-TWC) (bank 1) during stoichiometric air/fuel ratio feedback control. The powertrain control module (PCM) controls the air/fuel ratio from the rear air/fuel ratio (A/F) sensor (bank 1, sensor 1) output voltage so that the rear WU-TWC (bank 1) efficiency is optimized. When power is applied to the rear secondary HO2S (bank 1, sensor 2) heater, if the rear secondary HO2S (bank 1, sensor 2) output voltage is high or the SO2SGB1 terminal voltage is high during feedback control, the PCM detects a malfunction and stores a DTC.