LEMON Manuals: Even more car manuals for everyone
Home >> GMC >> 1991 >> Value Van 7.4 N >> Repair and Diagnosis >> External Pages >> Different car >> Section 43 (Engine Controls - Tests W/Codes - 8.0L) >> Self-Diagnostic Tests >> Test NTC-7B - Checking O2S Switching

Test NTC-7B - Checking O2S Switching

WARNING: This page is about a different car, the 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 diagrams, see WIRING DIAGRAMS  section at the end of this article.
  1. Disconnect right O2S connector. Ensure engine speed is more than 1500 RPM. Using scan tool, read LT O2S voltage. If LT O2S voltage is switching between less than 0.4 volt and more than 0.6 volt, reconnect right O2S connector. System is operating properly. Test passed. If LT O2S voltage is not switching as specified, go to next step.
  2. If LT O2S voltage stays less than 0.4 volt, go to step 5). If LT O2S voltage does not stay less than 0.4 volt, turn engine off. Release fuel pressure. Install a fuel pressure gauge to fuel rail test port. Turn ignition on. Using scan tool, actuate fuel system. Allow fuel pressure to stabilize. Go to next step.
  3. Stop fuel system actuation. Monitor fuel gauge for one minute. If fuel pressure drops to less than 25 psi (1.8 kg/cm2 ), replace leaking injector(s) as necessary. Perform TEST VER-2.
  4. If fuel pressure does not drop to less than 25 psi (1.8 kg/cm2 ), inspect air filter and air inlet ducts for restrictions. Clean restricted air inlet system as necessary. Perform TEST VER-2. If no restrictions exist, go to TEST NTC-18A.
  5. Allow engine to idle. Inspect engine for abnormal vacuum conditions. Repair abnormal vacuum conditions as necessary. Perform TEST VER-2. If no abnormal vacuum conditions exist, go to next step.
  6. Using scan tool, read LT O2S voltage. If LT O2S voltage does not stay less than 0.1 volt, go to step 8). If LT O2S voltage stays less than 0.1 volt, turn ignition off. Disconnect left O2S connector. Go to next step.
  7. Disconnect Powertrain Control Module (PCM) connector. Using scan tool in ohmmeter mode, check resistance of PCM connector terminal No. 23, left O2S signal circuit (Tan/White wire). If resistance is less than 5 ohms, repair short to ground in Tan/White wire. Perform TEST VER-2. If resistance is more than 5 ohms, replace left O2S. Perform TEST VER-2.
  8. Turn engine off. Replace left O2S. Turn ignition on. Using scan tool, reset adaptive fuel memory. Start engine. Allow engine to reach operating temperature. Using scan tool, read LT O2S voltage. If LT O2S voltage is switching between less than 0.4 volt and more than 0.6 volt, repair is complete. Perform TEST VER-2. If LT O2S voltage is not switching as specified, reconnect right O2S connector. Go to TEST NTC-18A.
scientia non olet · About LEMON Manuals