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Circuit/System Testing

WARNING: This page is about a different car, the 2020 Cadillac CT4. However, it is still accessible from the selected car via links, so may be relevant.

Test 1

  1. Ignition/Vehicle & All vehicle systems - Off
  2. Disconnect the electrical connector:M40 Rear Compartment Lid Latch
  3. Verify a test lamp illuminates between ground circuit terminal 2 and B+.
    • If the test lamp does not illuminate 
    1. Repair the open/high resistance on circuit 1650 or the ground connection.
    • Go to next step: If the test lamp illuminates 
  4. Connect a test lamp between the test points:Control circuit terminal 1 & ground
  5. Ignition - On / Vehicle - In Service Mode
  6. Operate the component:E7 Rear License Plate Lamp - Pressed

    Verify the test lamp state:

    Not used=Test lamp Off

    Pressed=Test lamp flashes ON and OFF

    • If the test lamp is always OFF 
    1. Ignition OFF, remove the test lamp, disconnect the harness connector at the K9 Body Control Module
    2. Test for infinite resistance between the control 6128 and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • Go to next step: If infinite resistance
    3. Test for less than 2 Ω in the control 6128 end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K9 Body Control Module
    • If the test lamp is always ON 
    1. Ignition OFF, remove the test lamp, disconnect the harness connector at the K9 Body Control Module.
    2. Test for less than 1 V between the control 6128 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K9 Body Control Module
    • Go to next step: If the test lamp turns ON and OFF 
  7. Test or replace the component:M40 Rear Compartment Lid Latch

Test 2

  1. Ignition/vehicle OFF, disconnect the connector at the E7 Rear License Plate Lamp
  2. Verify a test lamp illuminates between ground circuit terminal 1 and B+.
    • If the test lamp does not illuminate 
    1. Repair the open/high resistance on circuit 1650 or the ground connection.
    • Go to next step: If the test lamp illuminates 
  3. Ignition/vehicle On.
  4. Verify the M40 Rear Compartment Lid Latch is not Active
    • If Active 
    1. Test the circuit 5797 for a short to ground
      • If a short to ground is found, repair the fault on the circuit.
      • Go to next step: If a short to ground is not found.
    2. Replace the K9 Body Control Module.
    • Go to next step: If Inactive 
  5. Momentarily install a 3 A fused jumper wire between the signal circuit terminal 3 and ground.
  6. Verify the component produces a clicking sound:M40 Rear Compartment Lid Latch
    • If the component does not produce a sound and the 3 A fuse is OK 
    1. Test the circuit 5797 for an open/high resistance.
      • If an open/high resistance is found, repair the fault on the circuit.
      • Go to next step: If an open/high resistance is not found.
    2. Replace the K9 Body Control Module.
    • If the component does not produce a sound and the 3 A fuse is open 
    1. Test the circuit 5797 for a short to voltage.
      • If a short to voltage is found, repair the fault on the circuit.
      • Go to next step: If a short to voltage is not found.
    2. Replace the K9 Body Control Module.
    • Go to next step: If the component produces a sound 
  7. Replace the E7 Rear License Plate Lamp

Test 3

  1. Ignition/vehicle OFF, disconnect the connector at the S58B Rear Compartment Lid Release Switch - Interior.
  2. Verify a test lamp illuminates between ground circuit terminal 2 and B+.
    • If the test lamp does not illuminate 
    1. Repair the open/high resistance on circuit 2150 or the ground connection.
    • Go to next step: If the test lamp illuminates 
  3. Ignition/vehicle On.
  4. Verify the M40 Rear Compartment Lid Latch is not Active
    • If Active 
    1. Test the circuit 6189 for a short to ground
      • If a short to ground is found, repair the fault on the circuit.
      • Go to next step: If a short to ground is not found.
    2. Replace the S79D Front Side Door Window Control Switch - Driver
    • Go to next step: If Inactive 
  5. Momentarily install a 3 A fused jumper wire between the signal circuit terminal 3 and ground.
  6. Verify the component produces a clicking sound:M40 Rear Compartment Lid Latch
    • If the component does not produce a sound and the 3 A fuse is OK 
    1. Test the circuit 6189 for an open/high resistance.
      • If an open/high resistance is found, repair the fault on the circuit.
      • Go to next step: If an open/high resistance is not found.
    2. Replace the S79D Front Side Door Window Control Switch - Driver
    • If the component does not produce a sound and the 3 A fuse is open 
    1. Test the circuit 6189 for a short to voltage.
      • If a short to voltage is found, repair the fault on the circuit.
      • Go to next step: If a short to voltage is not found.
    2. Replace the S79D Front Side Door Window Control Switch - Driver
    • Go to next step: If the component produces a sound 
  7. Replace the S58B Rear Compartment Lid Release Switch - Interior.
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