DTC P0134: O2S1 Circuit - Insufficient Activity: Description

Oxygen Sensor (O2S) is used to determine oxygen content of exhaust. Oxygen content of exhaust indicates when engine is operating lean or rich. When engine is operating lean, exhaust will have more oxygen content. Once at operating temperature, O2S will produce a voltage in relation to the oxygen content of the exhaust. O2S requires an operating temperature of 600°F (360°C) to produce voltage. O2S will produce more voltage when exhaust is rich and less voltage when exhaust is lean. O2S operating voltage range is 0.1-1 volt (100-1000 mV).

The Powertrain Control Module (PCM) supplies a bias or reference voltage to O2S. This bias voltage is around 450 millivolts. The Alternative Fuels Engine Control Module (AF ECM) monitors the bias voltage as well as the voltage produced by the O2S.

During normal closed loop fuel control operation, AF ECM will add fuel (enriches mixture) when O2S indicates a lean exhaust condition. When O2S indicates a rich exhaust content, AF ECM will subtract fuel (lean-out mixture). This oscillation greater than and less than reference voltage (sometimes referred to as activity or switching) can be monitored using O2S signal voltage.

This DTC is used to indicate an O2S with inactive signal voltage.