Oxygen Sensor Diagnosis

The fuel control Oxygen Sensor (O2S) 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 Heated Oxygen Sensor (HO2S) 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 approx. 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 wire(s). Any attempt to repair the wires, connector or terminals could result in the obstruction of the reference air and degrade the oxygen sensor performance.