Circuit Description

The DTC P0134 Heated Oxygen Sensor (HO2S) Circuit Insufficient Activity Sensor 1 diagnostic monitors the HO2S switching time. The HO2S produces a voltage that varies between 100 mV and 900 mV under normal operating conditions. The Powertrain Control Module (PCM) monitors this voltage and determines if the exhaust is indicating a lean or rich fuel mixture. If the voltage input at the PCM is about 100 mV the fuel mixture is lean, and if the voltage input is about 900 mV the fuel mixture is rich. The PCM constantly monitors the HO2S signal during Closed Loop operation and compensates for a rich or a lean condition by decreasing or increasing the fuel injector pulse width as necessary. If the HO2S 1 voltage remains at or about 450 mV for an extended period of time, DTC P0134 will be set.