Checking

Oxygen Sensor (O2S) Control, Checking

Function of O2S control before Three Way Catalytic Converter (TWC)

NOTE:
- Oxygen sensor compares oxygen content of air with residual oxygen content in exhaust and delivers a voltage signal to the control module.
- The voltage signal "mixture rich (too little residual oxygen)" is 0.7 to 1.1 V (relative to reference Ground -GND-).
- The voltage signal "mixture lean (too much residual oxygen)" is -0.1 to +0.3 V (relative to reference Ground -GND-).
- At the transition from "rich" to "lean" and vice versa ( = 1.0) voltage will jump from between 0.7 and 10.1 V to between -0.1 and +0.3.3 V (or vice versa).
- Due to the steep voltage jump, oxygen sensor control cannot maintain the ideal mixture of = 1.0 as constant. Oxygen sensor control constantly fluctuates back and forth between the conditions "slightly too lean" and "slightly too rich".
- If voltage change does not occur or occurs only slowly, the following malfunctions could be present:
- Slits or holes in sensor head clogged.
- Sensors suffered thermal overload.
- Transition resistance in signal wire or Ground (GND) wire.
- Sensor too cold, sensor heating not functioning.
- Sensor damaged by contact spray or similar substance (contact spray is drawn through the fine hollow interiors by thermal fluctuations and capillary action into the electrical wiring in sensor).
- Sensor damaged by silicon vapors (the use of sealants containing silicon leads to trace elements of silicon being taken in by the engine. These silicon elements are not combusted and damage the oxygen sensor).