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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-2B - Checking Overdrive Circuit

Test NTC-2B - 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. Using scan tool, ensure transmission temperature is between 69°F (21°C) and 275°F (135°C). If transmission temperature is not between 69°F (21°C) and 275°F (135°C), replace transmission temperature sensor and retest vehicle for overdrive operation. Perform TEST VER-1.
  2. If transmission temperature is between 69°F (21°C) and 275°F (135°C), ensure throttle lever is fully closed and against idle speed screw. Using scan tool, read Throttle Position (TP) sensor voltage. If TP sensor voltage is not 0.89-1.20 volts, adjust or replace TP sensor. Retest vehicle for overdrive operation. Perform TEST VER-1.
  3. If TP sensor voltage is 0.89-1.20 volts, read overdrive switch state using scan tool. 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, go to next step.
  4. Turn ignition off. Disconnect PCM connector. Using scan tool in ohmmeter mode, check resistance of Powertrain Control Module (PCM) connector terminal No. 10, overdrive switch sense circuit (Orange/White wire). Turn overdrive switch on and off while observing scan tool. If scan tool display switches between less than 5 ohms and more than 5 ohms, replace PCM. Perform TEST VER-1.
  5. If scan tool display does not change between less than 5 ohms and more than 5 ohms, disconnect overdrive switch harness connector. Using scan tool in ohmmeter mode, check resistance of PCM connector terminal No. 10, overdrive switch sense circuit (Orange/White wire).
  6. If resistance is less than 5 ohms, repair short to ground in Orange/White wire. Perform TEST VER-1. If resistance is 5 ohms or more, replace overdrive switch. Perform TEST VER-1.
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