LEMON Manuals: Even more car manuals for everyone
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-8A - Checking Oxygen Sensor Switching

Test NTC-8A - Checking Oxygen 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. Operate engine at normal operating temperature. Using scan tool, read Oxygen Sensor (O2S) state. If O2S state switches, O2S is okay. Test is complete. If O2S state does not switch and sensor is locked on lean, go to TEST NTC-8B. If O2S state does not switch and sensor is not locked on lean, turn ignition off.
    NOTE: Before opening any part of Compressed Natural Gas (CNG) fuel system for repair, fuel pressure must be released. See FUEL PRESSURE RELEASE  .
  2. Turn ignition on. Using scan tool, monitor fuel pressure for 10 seconds. If fuel pressure drops more than 5 psi, go to next step. If fuel pressure does not drop more than 5 psi, inspect air cleaner filter and inlet ducts for restrictions. Repair as necessary. Perform TEST VER-2. If restrictions are not present, go to TEST NTC-15A.
  3. Inspect fuel rail and fuel lines for leaks. Release fuel pressure and repair as necessary. Perform TEST VER-2. If Fuel rail and fuel lines are okay, release fuel pressure and replace leaking injectors or "O" rings as necessary. Perform TEST VER-2.
scientia non olet · About LEMON Manuals