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Home >> GMC >> 1991 >> Value Van 7.4 N >> Repair and Diagnosis >> External Pages >> Different car >> Section 47 (Engine Controls - Tests W/Codes - 5.9L Diesel) >> Self-Diagnostic Tests >> Test NTC-2A - Checking Overdrive Circuit

Test NTC-2A - Checking Overdrive Circuit

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. If vehicle fails to go into overdrive, perform TEST NTC-2B. If vehicle goes into overdrive, ensure coolant temperature is more than 69°F (21°C) before proceeding. Using scan tool, read overdrive switch state.
  2. Turn overdrive switch on and off while observing scan tool display. If overdrive switch state changes between 4 ALLOW and 3 SPD, repair transmission as necessary. Perform TEST VER-1. If overdrive switch state does not change between 4 ALLOW and 3 SPD, turn ignition off.
  3. Disconnect Powertrain Control Module (PCM) connector. Using scan tool in ohmmeter mode, check resistance of PCM connector terminal No. 10, overdrive switch sense circuit (Orange/White wire). Turn overdrive switch on and off while observing scan tool display. If display changes from less than 5 ohms to more than 5 ohms, replace PCM. Perform TEST VER-1.
  4. If display does not change from less than 5 ohms to more than 5 ohms, disconnect overdrive switch harness connector. Using an external ohmmeter, check resistance in overdrive switch sense circuit (Orange/White wire) between overdrive switch connector and PCM connector terminal No. 10.
  5. If resistance is more than 5 ohms, repair open Orange/White wire. Perform TEST VER-1. If resistance is 5 ohms or less, replace overdrive switch. Perform TEST VER-1.