OXYGEN SENSOR CHECK <VEHICLES WITH CATALYTIC CONVERTER>

1.Disconnect the oxygen sensor connector and connect the special tool Test harness (MB991316) to the connector on the oxygen sensor side. 2.Measure resistance between terminal No. 1 and No. 3 on the oxygen sensor connector. Standard value: 11 - 18 Ω (at 20°C) 3.If there is no continuity, replace the oxygen sensor. 4.Warm up the engine until engine coolant is 80°C or higher.

5.Perform a tracing for 5 minutes or more with the engine speed of 2,500 r/min. 6.Connect a digital voltage meter between terminal No. 2 and No. 4. 7.While repeatedly racing the engine, measure the oxygen sensor output voltage. Standard value: Engine Oxygen sensor output voltage Remarks When racing the engine 0.6 - 1.0 V If you make the air/fuel ratio rich by racing the engine repeatedly, a normal oxygen sensor will output a voltage of 0.6 - 1.0 V. caution Be very careful when connecting the jumper wire; incorrect connection can damage the oxygen sensor. Be careful the heater is broken when voltage of beyond 12 V is applied to the oxygen sensor heater. note If the sufficiently high temperature (of approximate 400°C or more) is not reached although the oxygen sensor is normal, the output voltage would be possibly low although the rich air-fuel ratio. Therefore, if the output voltage is low, use a jumper wire to connect the terminal No. 1 (to be the red clip of special tool) and the terminal No. 3 (to be the blue clip of special tool) of the oxygen sensor with a (+) terminal and (-) terminal of 12 V power supply respectively, then check again. 8.If the sensor is defective, replace the oxygen sensor. note For removal and installation of the oxygen sensor, refer to GROUP 15 - Exhaust Manifold .