Checking the oxygen sensor in the exhaust gases (VW Passat B4)

Warm up the engine to a temperature of at least 80°C, check that the idle speed corresponds to the required value, ensure that the exhaust system is tight, ensure that the coolant temperature sensor is connected and that the supply voltage of the exhaust oxygen sensor corresponds to the required value.

Let the engine idle for at least 2 minutes.

Check the carbon monoxide (CO) content in the exhaust gases. Disconnect the fuel pressure regulator hose from the throttle body and close the hose. The carbon monoxide content in the exhaust gases should first increase briefly, then decrease again to normal. Connect the hose to the throttle body. If the CO content in the exhaust gases does not decrease, disconnect the connector (fig. 2-117) oxygen content sensor in the exhaust gases. Connect the connector terminal shown by the arrow in the figure alternately to the "plus" of the battery and to the "ground", monitor the change in the CO content in the exhaust gases. If the CO content does not increase or decrease, replace the oxygen content sensor in the exhaust gases.



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