Chrysler
Type:
    Powertrain - Fuel and Air Metering - ISO/SAE Controlled
Description:
    HO2S Remains At Center Conditions:
Cause:
    Engine runtime over 2 minutes in closed loop, ECT sensor input more than 176°F, then the test started and the PCM applied 5v to the rear HO2S-12 circuit for 30 seconds and then detected that the rear HO2S-12 signal was fixed between 0.39v to 0.52v (condition met for 30 seconds).

Generic
Type:
    Powertrain - Fuel and Air Metering - ISO/SAE Controlled
Description:
    O2 Sensor Circuit No Activity Detected

GM
Type:
    Powertrain - Fuel and Air Metering - ISO/SAE Controlled
Description:
    HO2S Circuit Open/Inactive Conditions
Cause:
    No Engine Sensor or Misfire codes set, engine runtime 1 minute, ECT input above 140°F, in closed loop A/F ratio at 14.7:1, throttle angle off idle over 6.5%, then the PCM detected that the HO2S-12 signal remained from 391-491 mv, condition met for 90 seconds