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Home >> GMC >> 1991 >> Value Van 7.4 N >> Repair and Diagnosis >> External Pages >> Different car >> Section 24 (Engine Controls - Tests W/Codes - 2.5L) >> Self-Diagnostic Tests >> Test NTC-7B - Checking Oxygen Sensor (O2S) Switching

Test NTC-7B - Checking Oxygen Sensor (O2S) Switching

WARNING: This page is about a different car, the 1995 Dodge Dakota. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: For circuit and connector terminal identification, see CONNECTOR IDENTIFICATION . For wiring diagrams, see WIRING DIAGRAM  section at the end of this article.
  1. Allow engine to idle. Inspect engine for vacuum leaks. Repair vacuum leaks as necessary. Perform TEST VER-2. If no vacuum leaks exist, using scan tool, read O2S 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 O2S connector. Disconnect Powertrain Control Module (PCM) connector. Put scan tool in ohmmeter mode. Using scan tool, check resistance of O2S connector Black/Dark Green wire.
  3. If resistance is less than 10 ohms, repair short to ground in Black/Dark Green wire. Perform TEST VER-2. If resistance is more than 10 ohms, replace O2S. Perform TEST VER-2.
  4. Turn engine off. Replace O2S. Turn ignition on. Using scan tool, reset adaptive fuel memory. Start engine. Allow engine to reach normal operating temperature.
  5. Using scan tool, read O2S state. If O2S state is switching, repair is complete. Perform TEST VER-2. If O2S state is not switching, go to TEST NTC-15A.
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