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Circuit/System Testing

WARNING: This page is about a different car, the 2021 GMC Sierra 3500 HD and 2021 GMC Sierra 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:

It may take up to 2 min for all vehicle systems to power down before an accurate ground or low reference circuit continuity test can be performed.

Keyless Entry Transmitter

  1. Ignition/Vehicle & All vehicle systems - Off
  2. Keyless Entry Transmitter - All Doors Lock
    • If none of the components work properly 
    1. Replace the component: Battery @ Keyless Entry Transmitter
    2. Keyless Entry Transmitter - All Doors Lock
    3. Exterior Driver Door Handle Switch/Exterior Passenger Door Handle Switch/Trunk Lid/Liftgate Window Exterior Unlatch Switch - Open
      • If none of the components work properly - Replace the component: Keyless Entry Transmitter
      • Go to next step: If all components operate
    4. All OK.
    • Go to next step: If all components operate 
  3. Many instances of "No Transponder Detected"conditions are related to external environmental influences, in most cases some form of radio frequency interference. If that is suspected, question the customer about the conditions or locations where the condition occurs. If the condition is caused by external influences, the system operates as designed and there is no actual fault that could be diagnosed with this procedure. External environmental influences may include:
    • Flat screen televisions
    • Darkness sensing exterior lights
    • Cell phones and cell phone chargers
    • Power inverters
    • Gas stations with pay-at-the-pump radio frequency transponders
    • Any area with high radio frequency traffic. For example airports, police stations and fire stations.

Antenna Malfunction

    NOTE:

    It may take up to 2 min for all vehicle systems to power down before an accurate ground or low reference circuit continuity test can be performed.

  1. Ignition/Vehicle & All vehicle systems - Off
  2. Disconnect the appropriate electrical connector: T10 Keyless Entry Antenna
  3. Ignition On - Engine Off
  4. Test for less than 1 V between the test points: Terminal 1 & Ground
    • If 1 V or greater 
    1. Ignition/Vehicle & All vehicle systems - Off
    2. Disconnect the electrical connector: K84 Keyless Entry Control Module
    3. Ignition/Vehicle - On
    4. Test for less than 1 V between the test points: Signal circuit & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • If less than 1 V - Replace the component: K84 Keyless Entry Control Module
    • Go to next step: If less than 1 V 
  5. Ignition/Vehicle & All vehicle systems - Off
  6. Connect a DMM between the test points: Terminal 1 & Ground
  7. Measure = Voltage - (min/max)
  8. Keyless Entry Transmitter - All Doors Lock
  9. Exterior Driver Door Handle Switch/Exterior Passenger Door Handle Switch/Trunk Lid/Liftgate Window Exterior Unlatch Switch - Open
    • If less than 1 V 
    1. Ignition/Vehicle & All vehicle systems - Off
    2. Disconnect the electrical connector: K84 Keyless Entry Control Module
    3. Test for infinite resistance between the test points: Signal circuit & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • Go to next step: If infinite resistance 
    4. Test for less than 2 ohms between the test points: Signal circuit @ Component harness & The other end of the circuit
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Replace the component: K84 Keyless Entry Control Module
    • Go to next step: If greater than 1 V 
  10. Test for less than 1 V between the test points: Terminal 2 & Ground
    • If 1 V or greater 
    1. Ignition/Vehicle - Off
    2. Disconnect the electrical connector: K84 Keyless Entry Control Module
    3. Test for less than 1 V between the test points: Low Reference circuit & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • If less than 1 V - Replace the component: K84 Keyless Entry Control Module
      • Go to next step: If less than 1 V 
  11. Ignition/Vehicle & All vehicle systems - Off
  12. Connect a DMM between the test points: Terminal 2 & Ground
  13. Measure = Voltage - (min/max)
  14. Keyless Entry Transmitter - All Doors Lock
  15. Exterior Driver Door Handle Switch/Exterior Passenger Door Handle Switch/Trunk Lid/Liftgate Window Exterior Unlatch Switch - Open
    • If less than 1 V 
    1. Ignition/Vehicle & All vehicle systems - Off
    2. Disconnect the electrical connector: K84 Keyless Entry Control Module
    3. Test for infinite resistance between the test points: Low Reference circuit & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • Go to next step: If infinite resistance 
    4. Test for less than 2 ohms between the test points: Signal circuit @ Component harness & The other end of the circuit
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Replace the component: K84 Keyless Entry Control Module
    • Go to next step: If greater than 1 V 
  16. Replace the appropriate component: T10 Keyless Entry Antenna
  17. Keyless Entry Transmitter - All Doors Lock
  18. Exterior Driver Door Handle Switch/Exterior Passenger Door Handle Switch/Trunk Lid/Liftgate Window Exterior Unlatch Switch - Open
    • If none of the components work properly 

      Replace the component: K84 Keyless Entry Control Module

    • Go to next step: If all components operate 
  19. All OK.
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