Catalyst Monitor Oxygen Sensors
SCAN TOOL TESTINGThe Rear Heated Oxygen Sensor (HO2S 2) is used on California vehicles only and is used to monitor the oxygen storage capability of the catalytic converter. Similar to the O2S, the HO2S 2 reacts with the oxygen content in the exhaust stream to produce a voltage signal only after the catalytic converter. Unlike the O2S, the HO2S 2 is normal when it's activity appears lazy or inactive. A scan tool can be used to diagnose the HO2S 2 but should be replaced only when directed to by a diagnostic chart. Testing and Inspection