Heated Oxygen Sensor (HO2S)

On all 1998 models and 1999 XJR, an HO2S is located upstream of each catalytic converter (total of 2). On all other models, an HO2S is located upstream and downstream of each catalytic converter (total of 4). HO2S provide input to the ECM or PCM proportional to the oxygen content of the exhaust gases leaving the engine. Heater element improves response time of the sensor during warm-up.