Detection Condition
WARNING: This page is about a different car, the 2003 Mazda Tribute. However, it is still accessible from the selected car via links, so may be relevant.
- DTC P0040 or P1128 indicates during KOER testing the front HO2S signal(s) response for a fuel shift to the correct engine bank was not indicated.
- DTC P0041 or P1129 indicates during KOER testing the rear HO2S signal(s) response for a fuel shift to the correct engine bank was not indicated.
HO2S detects presence of oxygen in exhaust and produces a variable voltage according to the amount of oxygen detected. A high concentration of oxygen in the exhaust produces a low voltage signal (less than 0.4 volt). A low concentration of oxygen in the exhaust produces 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.