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Home >> GMC >> 1991 >> Value Van 7.4 N >> Repair and Diagnosis >> External Pages >> Different car >> Section 29 (Engine Controls - Tests W/Codes - 3.3L Gasoline) >> Self-Diagnostic Tests >> Test NTC-7B - Checking Oxygen (O2) Sensor Switching

Test NTC-7B - Checking Oxygen (O2) Sensor Switching

WARNING: This page is about a different car, the 1995 Plymouth Voyager, 1995 Plymouth Grand Voyager, 1995 Dodge Grand Caravan, and 1995 Dodge Caravan. However, it is still accessible from the selected car via links, so may be relevant.
  1. Allow engine to idle. Inspect engine for vacuum leaks. Repair vacuum leaks as necessary. Perform TEST VER-2. If no vacuum leaks exist, use scan tool to read O2 sensor signal voltage.
  2. If voltage is more than 0.1 volt, go to step 4). If voltage is less than 0.1 volt, turn ignition off. Disconnect O2 sensor connector. Disconnect Powertrain Control Module (PCM) connector. Using scan tool in ohmmeter mode, check resistance of O2 sensor connector (harness side), signal circuit (Dark Green/White wire).
  3. If resistance is less than 10 ohms, repair short to ground in Dark Green/White wire. Perform TEST VER-2. If resistance is more than 10 ohms, replace O2 sensor. Perform TEST VER-2.
  4. Turn engine off. Replace O2 sensor. Turn ignition on. Using scan tool, reset adaptive fuel memory. Start engine. Allow engine to reach normal operating temperature.
  5. Using scan tool, read O2 sensor state. Set engine speed to more than 1500 RPM. If O2 sensor state is switching, repair is complete. Perform TEST VER-2. If O2 sensor state is not switching, go to TEST NTC-16A.
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