The oxygen sensor (O2 sensor) is a ceramic zirconia bulb which produces an electrical voltage when exposed to the oxygen. The sensor is mounted in the exhaust manifold and is used to detect the amount of oxygen present in the exhaust stream. When there is a large amount of oxygen present (lean mixture), the sensor produces a low voltage. When there is a lesser amount present (rich mixture) it produces a higher voltage.
The O2S must reach an operating temperature of approximately 600°F (315°C), in order to function properly. Some sensors contain an electrical heating element to speed up the warm-up time during cold engine operation, and to ensure the sensor remains functional during all phases of engine operation. Sensors using an internal heater are commonly referred to as Heated Oxygen Sensors or HO2S.
Front Mounted Sensors
The ECM uses the signal received from the front mounted oxygen sensor, to maintain an ideal fuel mixture of 14.7:1. Since the oxygen sensor is able to rapidly detect oxygen changes in the exhaust and convert it to electrical voltage, the sensor acts as a rich-lean switch. The ECM continually monitors the oxygen sensor's signal and corrects the air/fuel mixture accordingly, thus maintaining the optimum air/fuel mixture.
Rear Mounted Sensors
Beginning in 1995, the GA16DE and SR20DE engines use a second oxygen sensor, mounted after the TWC converter assembly. This sensor, known as a Rear HO2S, uses the same operating principles as front mounted sensors mounted. The major difference between the sensors is the purpose they serve. Unlike front mounted sensors, rear mounted sensors have no effect on the fuel management system. The On Board Diagnostic (OBD) system uses the signal received from the rear mounted sensor is to detect the efficiency of the TWC converter.
You will need a special socket to do this.
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V W
Master Tech .
30 years/Master Tech. Foreign and Domestic