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Home >> Volkswagen >> 1993 >> Fox Base, 1.8 B >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests >> Fuel System >> Oxygen (O2) Sensor Control >> Fox 1.8L Digifant I (California)
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Fox 1.8L Digifant I (California)

  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 is okay. Turn ignition off.
  2. Connect Scan Tester (VAG 1551) to Data Link Connectors (DLC) located in center console. Start engine and allow it to idle. With scan tester in READ MEASURING VALUE BLOCK function, ensure coolant temperature is more than 176°F (80°C) as displayed in channel No. 3 of scan tester. Value should be 11.
  3. Allow engine to run for 2 minutes at idle. Read oxygen (O2) sensor signal in channel No. 5 of scan tester. If oxygen (O2) sensor control circuit is okay, display value varies by more than 14.
  4. If display value is 0-5, check for a short to battery voltage in oxygen (O2) sensor control circuit using next step. If display value is 164-168, check for an open circuit in oxygen (O2) sensor control circuit using step 6). If display value is 230 or more, check for a short to ground in oxygen (O2) sensor control circuit using step 8).
  5. Disconnect oxygen (O2) sensor connector (on valve cover). If scan tester value is now 164-168, replace oxygen (O2) sensor (oxygen (O2) sensor control circuit is okay). If value is not 164-168, check wiring harness for a short circuit to battery voltage between sensor and ECM. If wiring harness is okay, replace ECM. After repairs, erase fault memory.
  6. Disconnect oxygen (O2) sensor connector (on valve cover). Ground oxygen (O2) sensor wiring harness connector Violet wire. If scan tester value is now 230 or more, replace oxygen (O2) sensor (oxygen (O2) sensor control circuit is okay).
  7. If value is not at least 230, check wiring harness for an open circuit between sensor and ECM. If wiring harness is okay, replace ECM. After repairs, erase fault memory.
  8. Disconnect oxygen (O2) sensor connector (on valve cover). If scan tester value is now 164-168, replace oxygen (O2) sensor (oxygen (O2) sensor control circuit is okay). If value is not 164-168, check wiring harness for a short circuit to ground between sensor and ECM. If wiring harness is okay, replace ECM. After repairs, erase fault memory.
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