Del Sol L4-1.5L SOHC (1993)
Heated Oxygen Sensor: Description and Operation
Oxygen Sensor and Output Chart
PURPOSE
The Engine Control Module (ECM) uses the O2 signal to fine tune the Fuel Injector duration to maintain the correct fuel mixture.
OPERATION
The Oxygen Sensor is mounted to the Exhaust Manifold or pipe with the sensor end extending into the exhaust stream. It uses zirconia and platinum to
compare exhaust oxygen content with that of the outside air.
When heated by the combination of its internal heater and exhaust gases, the sensor supplies a low voltage signal (0.0 - 1.0 volt) to the Engine Control
Module. When the engine is running rich, the oxygen differential is relatively high so signal voltage increases. When a lean condition occurs the
difference in oxygen content is much lower causing a lower voltage signal to be produced.
Oxygen sensor operation is monitored by the Engine Control Module (ECM) and a malfunction should be accompanied by a Diagnostic Trouble
Code (DTC). Circuit and output testing procedures are covered in detail in the Diagnostic Trouble Code Charts. See: Testing and Inspection
Oxygen Sensor malfunctions will cause increased emission output and smog check failure. Other symptoms may include poor idle quality or poor fuel
economy.
HINT: When monitoring oxygen sensor operation with an oscilloscope, watch for a sine wave with a frequency of at least 8 cycles in 10 seconds. A
"lazy" oxygen sensor will not always set a code, but will usually cause abnormal emissions levels.
