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Home >> GMC >> 1991 >> Value Van 7.4 N >> Repair and Diagnosis >> External Pages >> Different car >> Section 41 (Engine Controls - Tests W/Codes - 5.9L Gasoline) >> Self-Diagnostic Tests >> Test NTC-8A - Checking O2S Heater

Test NTC-8A - Checking O2S Heater

WARNING: This page is about a different car, the 1995 Dodge Ram Wagon, 1995 Dodge Ram Van, 1995 Dodge Pickup, and 1995 Dodge Cab & Chassis. 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 diagram, see WIRING DIAGRAMS  section at the end of this article.
NOTE: BR body (heavy duty engine) is equipped with dual O2S. Scan tool displays dual O2S as LT O2S and RT O2S.
  1. On light duty engine, go to TEST NTC-8B. On BR body (heavy duty engine), turn ignition off. Disconnect right O2S connector. Turn ignition on. Using scan tool, actuate ASD fuel system. Wait 2 minutes for O2S voltage to stabilize.
  2. Using scan tool, read left O2S voltage. If left O2S voltage is more than 4.8 volts, go to next step. If left O2S voltage is less than 4.8 volts, stop ASD fuel system actuation. Reconnect right O2S connector. Go to step 5).
  3. Disconnect left O2S connector. Using scan tool in voltmeter mode, check voltage on left O2S connector (harness side) ASD relay output circuit (Dark Green/Orange wire). If voltage is more than 10 volts, go to next step. If voltage is less than 10 volts, repair open Dark Green/Orange wire. Perform TEST VER-2.
  4. Using scan tool, stop ASD fuel system actuation. Using scan tool in ohmmeter mode, check resistance on left O2S connector (harness side) heater ground circuit (Black/White wire). If resistance is more than 5 ohms, repair open Black/White wire. Perform TEST VER-2. If resistance is less than 5 ohms, replace left O2S. Perform TEST VER-2.
  5. Turn ignition on. Using scan tool, actuate ASD fuel system. Wait 2 minutes for right O2S voltage to stabilize. Using scan tool, read right O2S voltage. If voltage is less than 4.8 volts, O2S is functioning properly. Test is complete. If voltage is more than 4.8 volts, go to next step.
  6. Disconnect right O2S connector. Using scan tool in voltmeter mode, check voltage on right O2S connector (harness side), ASD relay output circuit (Dark Green/Orange wire). If voltage is less than 10 volts, repair open in Dark Green/Orange wire. Perform TEST VER-2.
  7. If voltage is more than 10 volts, use scan tool to stop ASD fuel system actuation. Using scan tool in ohmmeter mode, check resistance on right O2S connector (harness side), heater ground (Black/White wire). If resistance is more than 5 ohms, repair open Black/White wire. Perform TEST VER-2. If resistance is less than 5 ohms, replace right O2S. Perform TEST VER-2.
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