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Home >> GMC >> 1991 >> Value Van 7.4 N >> Repair and Diagnosis >> External Pages >> Different car >> Section 31 (Engine Controls - Tests W/Codes - 3.3L CNG) >> Self-Diagnostic Tests >> Test NTC-9A - Checking Oxygen Sensor Heater

Test NTC-9A - Checking Oxygen Sensor Heater

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. Turn ignition on. Using scan tool, actuate Auto Shutdown (ASD) fuel system. Wait 2 minutes for Oxygen Sensor (O2S) voltage to stabilize. Using scan tool, read O2S voltage. If voltage is 0.4-0.6 volt, system is functioning properly. Test is complete.
  2. If voltage is not 0.4-0.6 volt, disconnect O2S connector. Ensure scan tool is still actuating ASD fuel system. Using scan tool in voltmeter mode, check voltage on O2S connector, ASD relay output circuit (Dark Green/Black wire). If voltage is less than 10 volts, repair open Dark Green/Orange wire or Dark Green/Black wire. Perform TEST VER-2.
  3. If voltage is more than 10 volts, stop actuator test. Using scan tool in ohmmeter mode, check resistance of O2S connector, heater ground circuit (Black wire). If resistance is more than 5 ohms, repair open Black wire or Black/White wire. Perform TEST VER-2. If resistance is less than 5 ohms, replace O2S. Perform TEST VER-2.
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