Detection Condition

• DTC P0131 indicates HO2S11 (front right V6 or front 4-cylinder) has generated a negative voltage.
• DTC P0151 indicates HO2S21 (front left) has generated a negative voltage.

HO2S detects oxygen in the exhaust and produces a variable voltage according to the amount of oxygen detected (0.0-1.1 volts). A high concentration of oxygen in the exhaust causes HO2S to produce a low voltage signal (less than 0.4 volt). A low concentration of oxygen in the exhaust causes HO2S to produce a high voltage signal (more than 0.6 volt). HO2S provides feedback to PCM indicating air/fuel ratio in order to achieve near stoichiometric air/fuel ratio of 14.7:1 during closed loop engine operation.