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Home >> Cadillac >> 2021 >> XT5 Sport >> Repair and Diagnosis >> External Pages >> Different car >> Section 823 (Transfer Case - Mp 3023/3024 (NQH) - Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> Transfer Case Neutral Indicator Malfunction >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2023 GMC Sierra 3500 HD and 2023 GMC Sierra 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition/Vehicle - Off
  2. Disconnect the electrical connector: S126 Drive Mode Select Switch
  3. Ignition - On/Vehicle - In Service Mode
  4. Verify a test lamp turns On between the test points: Control circuit terminal 6@Component harness & Ground
    • If the test lamp does not turn On 
    1. Ignition/Vehicle - Off
    2. Disconnect the electrical connector: K33 HVAC Control Module
    3. Ignition - On/Vehicle - In Service Mode
    4. Verify a test lamp does not turn On between the test points: Control circuit terminal 6@Component harness & Ground
      • If the test lamp turns On

        Replace the component: K33 HVAC Control Module

      • Go to next step: If the test lamp does not turn On
    5. Ignition/Vehicle - Off & Remove - Test lamp
    6. Disconnect the electrical connector: X5@K9 Body Control Module
    7. Test for infinite resistance between the test points: Control circuit terminal 6@Component harness & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • Go to next step: If infinite resistance
    8. Test for less than 2 ohms between the test points: Control circuit terminal 6@Component harness & Terminal 14 X5@Control module harness
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Replace the component: K9 Body Control Module
    • Go to next step: If the test lamp turns On 
  5. Connect a test lamp between the test points: Control circuit terminal 7@Component harness & B+
  6. Perform the scan tool control function: Transfer Case Neutral Range Indicator - On/Off

    Verify the test lamp turns On and Off.

    • If the test lamp is always Off 
    1. Ignition/Vehicle - Off & Remove - Test lamp
    2. Disconnect the electrical connector: K69 Transfer Case Control Module
    3. Ignition - On/Vehicle - In Service Mode
    4. Test for less than 1 V between the test points: Control circuit terminal 7@Component harness & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • Go to next step: If less than 1 V
    5. Ignition/Vehicle - Off
    6. Test for less than 2 ohms between the test points: Control circuit terminal 7@Component harness & Terminal 10@Control module harness
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Replace the component: K69 Transfer Case Control Module
    • If the test lamp is always On 
    1. Ignition/Vehicle - Off & Remove - Test lamp
    2. Disconnect the electrical connector: K69 Transfer Case Control Module
    3. Test for infinite resistance between the test points: Control circuit terminal 7@Component harness & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • If infinite resistance - Replace the component: K69 Transfer Case Control Module
    • Go to next step: If the test lamp turns On and Off 
  7. Test or replace the component: S126 Drive Mode Select Switch
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