Ford
Type:
    Powertrain - Fuel and Air Metering - ISO/SAE Controlled
Description:
    HO2S No Activity Circuit Conditions
Cause:
    Engine running in closed loop for 5 minutes, then the PCM detected that the HO2S failed the maximum or minimum voltage range check (middle signal out-of-range)

Generic
Type:
    Powertrain - Fuel and Air Metering - ISO/SAE Controlled
Description:
    O2 Sensor Circuit

GM
Type:
    Powertrain - Fuel and Air Metering - ISO/SAE Controlled
Description:
    HO2S Circuit Conditions
Cause:
    No AIR system or EVAP codes set, HO2S-12 indicating closed loop, system voltage over 11 v, AIR system not operating, AIR system test not running, engine runtime over 10 minutes, low fuel not indicated, TWC temperature less than 1472°F, then the PCM detected that the HO2S-22 signal was less than 40 mv