Chrysler
Type:
    Powertrain - Fuel and Air Metering - ISO/SAE Controlled
Description:
    HO2S Heater Circuit Conditions
Cause:
    Engine at idle after a cold startup, ECT sensor input less than 147°F, BTS ambient air input at ±59°F of ECT input, then test started and the PCM detected that the left front HO2S-21 signal was over 300 mv for 30-90 seconds.

Ford
Type:
    Powertrain - Fuel and Air Metering - ISO/SAE Controlled
Description:
    HO2S Heater Circuit Conditions
Cause:
    Engine running for 1 minute, then the PCM detected an open or short in the HO2S heater circuit

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

GM
Type:
    Powertrain - Fuel and Air Metering - ISO/SAE Controlled
Description:
    HO2S Heater Circuit Conditions
Cause:
    No CKP, ECT, EGR, EVAP, Fuel Trim, Fuel Injector, IAT, MAP, Misfire or TP sensor codes set, system voltage 8-18v, ECT and IAT inputs less than 95°F and within 11°F of each other at startup, average MAF sensor less than 20 g/sec, then the PCM detected the HO2S-21 signal remained within 150 mv of bias voltage during the test period (time varies between 42 seconds and 2 minutes)