HO2S heater

Turn off ignition switch and disconnect HO2S connector.
Check that voltage of HO2S connector (vehicle side) between terminals "4" and "3" is battery voltage when ignition switch is in ON position.
If faulty condition is found, check power supply circuit, ground circuit and connections.

Fig 1: Identifying HO2S Heater Connector Terminal
Courtesy of SUZUKI OF AMERICA CORP.
Using ohmmeter, measure resistance of HO2S connector (sensor side) of sensor heater between terminals "3" and "4" at sensor connector.
If faulty condition is found, replace HO2S.

NOTE: Sensor temperature affects resistance value largely. Make sure that sensor heater is at specified temperature.

HO2S heater resistance

5.0 - 6.4 Ω at 20 °C (68 °F)

Fig 2: Identifying HO2S Heater Connector Terminal
Courtesy of SUZUKI OF AMERICA CORP.