Heated Oxygen Sensor No. 1

Heated Oxygen Sensor No. 1 (HO2S1) is mounted in exhaust manifold in front of Warm-Up Three-Way Catalyst (WU-TWC). HO2S1 produces 100-900 mV. PCM uses HO2S1 voltage to determine exhaust gas oxygen content during engine operation. Low voltage indicates a lean air/fuel and a higher voltage indicates a rich air fuel mixture. HO2S1 works similar to a non-heated sensor, except HO2S1 is heated to operating temperatures during engine operation. For component locations, see Figure .