Detection Condition

DTC P0131 indicates HO2S-11 (front Bank 1 on 3.0L or front on 2.0L) has generated a negative voltage.

DTC P0151 indicates HO2S-21 (front Bank 2) has generated a negative voltage.

HO2S detects oxygen in the exhaust and produces a variable voltage according to the amount of oxygen detected. A high concentration of oxygen in the exhaust causes HO2S to produce a low voltage signal (less than 0.4 volts). A low concentration of oxygen in the exhaust causes HO2S to produce a high voltage signal (more than 0.6 volts). HO2S provides feedback to PCM indicating air/fuel ratio in order to achieve near stoichiometric air/fuel ratio during closed loop engine operation.