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Home >> Volkswagen >> 1993 >> Cabriolet Base, 1.8 C, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests >> Fuel System >> Oxygen (O2) Sensor Control >> Cabriolet 1.8L Digifant II (Federal)
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Cabriolet 1.8L Digifant II (Federal)

  1. Ensure engine coolant temperature is at least 176°F (80°C). Ensure there are no exhaust system leaks between cylinder head and catalytic converter. Ensure voltage to oxygen (O2) sensor heater and heater is okay. Ensure engine idle speed is okay.
  2. Disconnect 4-pin oxygen (O2) sensor connector (located on a bracket, next to valve cover). Using test leads from Adapter Kit (VAG 1594), connect DVOM between Red/White wire and Blue wire. Start engine and allow it to idle. DVOM reading must be battery voltage.
  3. Turn engine off and reconnect 4-pin oxygen (O2) sensor connector. Connect CO tester using Adapter (VAG 1363/3) on CO tap tube. DO NOT remove oxygen (O2) sensor. Start engine and allow it to idle for at least 2 minutes. Measure and record CO level.
  4. Disconnect fuel pressure regulator vacuum hose at intake manifold and plug opening. CO level must briefly increase then drop off. If CO level does not change, disconnect 4-pin oxygen (O2) sensor connector.
  5. Connect test lead to oxygen (O2) sensor wiring harness Violet wire terminal. Alternately connect other end of test lead to battery positive and negative terminals. CO level must increase or decrease.
  6. If CO level changes, replace oxygen (O2) sensor (oxygen (O2) sensor control circuit is okay). If CO level does not change, check oxygen (O2) sensor control circuit wiring harness for an open circuit using the appropriate PIN VOLTAGE CHARTS article in this section. If wiring harness is okay, replace ECM.
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