1.7.9 Operation readiness of the rear HO2S: Notes

The operation readiness diagnostic of the rear HO2S runs continuously and can detect faulty electrical connections. Heater circuit faults are monitored separately. Most of the checks use the measured voltage of the rear HO2S as an input for diagnosis. Fig 1 indicates the regions on the voltage versus normalized A/F ratio characteristic curve where malfunctions are detected.

Fig 1: Rear HO2S Output Voltage And A/F Ratio Graph

Courtesy of BMW OF NORTH AMERICA, INC.