Heated Oxygen Sensor-1

A malfunction in Heated Oxygen Sensor-1 (HO2S-1) circuit can set a related Diagnostic Trouble Code (DTC). For testing procedures, see TESTS W/CODES article. Use the following procedure to diagnose HO2S-1.

A voltage is produced in response to amount of oxygen in exhaust gases. A lean mixture (high oxygen content) will produce a low voltage of about 100 mV. A rich mixture (low oxygen content) will produce a high voltage of about 900 mV. Voltage reading (activity) should vary above idle.