Chrysler
Type:
    Powertrain - Fuel and Air Metering - ISO/SAE Controlled
Description:
    HO2S Shorted To Ground Conditions
Cause:
    ECT sensor over 170°F on previous key on, cold engine startup requirement met (ECT input under 98°F, BTS input within 27°F of ECT input), at idle speed, and PCM detected the HO2S-11 signal was less than 156 mv for 28 seconds.

Ford
Type:
    Powertrain - Fuel and Air Metering - ISO/SAE Controlled
Description:
    HO2S Circuit Low Voltage Conditions
Cause:
    Engine running in closed loop, then the PCM detected a negative HO2S voltage known as character shift downward Look for a contaminated HO2S

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

GM
Type:
    Powertrain - Fuel and Air Metering - ISO/SAE Controlled
Description:
    HO2S Circuit Low Input Conditions
Cause:
    No AIR, ECT, EVAP, IAT, Injector, MAF, MAP orTP sensor codes set, AIR, Catalyst and EGR Flow tests inactive, system voltage from 8-18v, engine runtime over 200 seconds, A/F ratio 14.4-14.9, throttle angle at 3-25%, closed loop enabled, conditions met for 3 seconds, then the PCM detected that the HO2S-21 signal remained fixed below 75 mv for about 95 seconds in normal closed loop fuel control, or the HO2S-21 signal remained below 575 mv for about 11 seconds during Power Enrichment fuel control