DTC P1134: Ho2S Transition Time Ratio (Bank 1; Sensor 1): Description

Heated Oxygen Sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The Powertrain Control Module (PCM) supplies the HO2S with a reference or bias voltage of about 450 mV. When engine is first started, PCM operates in Open Loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperatures and Closed Loop is achieved, the HO2S generates a voltage within a range of 0-1000 mV that fluctuates greater than and less than bias voltage. High HO2S voltage indicates a rich exhaust stream. Low HO2S voltage indicates a lean exhaust stream.

This diagnostic will only run once per ignition cycle. The PCM monitors the rich-to-lean and lean-to-rich transitions. A transition is defined as the HO2S voltage changes from greater than 600 mV to less than 300 mV or from less than 300 mV to greater than 600 mV. If PCM detects that the transition time ratio is not within a specified range, DTC P1134 will set.