5. Oxygen Sensor System

The oxygen sensor system provides the fuel injection system with information about combustion efficiency by measuring the oxygen content in the exhaust. The exhaust-mounted oxygen sensor is constructed of ceramic material coated with platinum. One surface is exposed to the exhaust gas, while the other is exposed to atmosphere. The difference in oxygen content between the two surfaces causes a chemical reaction which generates a low-voltage signal (100-1000mv). This signal is monitored by the control unit which, in turn, signals for changes in the air/fuel ratio in the fuel injection system.

Since the oxygen sensor system relies on low-voltage signals, it is very sensitive to contamination or poor connections. Making sure that the electrical contacts are clean and dry may cure system problems easily and preclude the need for time-consuming testing.

Because the oxygen sensor system is different for each fuel injection type, the repair information in this section is organized according to fuel injection type. For help in identifying the fuel injection system, see FUEL SYSTEM-GASOLINE.

Replacement of the oxygen sensor is a scheduled maintenance procedure. The specified replacement interval varies depending on model year. On 1985-1987 models, the sensor's replacement interval is signalled by an indicator light on the instrument panel coming on as a service reminder. After the oxygen sensor is replaced, the mileage counter must be reset. On 1988 and later models with oxygen sensors, the service reminder light has been omitted. See LUBRICATION AND MAINTENANCE for more information on the oxygen sensor replacement interval and the mileage counter resetting procedure.