Oxygen Sensor Diagnosis

The fuel control front heated oxygen sensor (HO2S1) is diagnosed for the following conditions:

• Slow response
• Response time, time to switch R/L or L/R
• Inactive signal, output steady at bias voltage approximately 450 mV
• Signal fixed high
• Signal fixed low

The catalyst monitor rear heated oxygen sensor (HO2S2) is diagnosed for the following conditions:

• Heater performance, time to activity on cold start
• Signal fixed low during steady state conditions or power enrichment, hard acceleration when a rich mixture should be indicated
• Signal fixed high during steady state conditions or deceleration mode, deceleration when a lean mixture should be indicated
• Inactive sensor, output steady at approximately 438 mV

If the oxygen sensor pigtail wiring, connector, or terminal are damaged, the entire oxygen sensor assembly must be replaced. Do not attempt to repair the wiring, connector, or terminals. In order for the sensor to function properly, it must have clean reference air provided to it. This clean air reference is obtained by way of the oxygen sensor wires. Any attempt to repair the wires, connector, or terminals could result in the obstruction of the reference air and degrade oxygen sensor performance.