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Home >> Cadillac >> 2021 >> CT4 Sport, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 228 (Vehicle Access System - Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> DTC B125D, B1800, or B1805 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2022 Cadillac CT4. However, it is still accessible from the selected car via links, so may be relevant.

Test 1

  1. Ignition/Vehicle - Off
  2. Disconnect the electrical connector: A23P Front Side Door Latch-Passenger
  3. Connect a test lamp between the test points: Control circuit terminal 8 & ground
  4. Ignition - On/Vehicle - In Service Mode
  5. Operate the component: S13D Door Lock Switch - Driver

    Verify the test lamp state:

    Not used = Test lamp Off

    Lock Switch - 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 2680 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 2680 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, ignition ON.
    2. Test for less than 1 V between the control 2680 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 
  6. Connect a test lamp between the test points: Control circuit terminal 9 & ground
  7. Ignition - On/Vehicle - In Service Mode
  8. Operate the component: S13D Door Lock Switch - Driver

    Verify the test lamp state:

    Not used = Test lamp Off

    Unlock - 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 2682 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 2682 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, ignition ON.
    2. Test for less than 1 V between the control 2682 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 
  9. Test or replace the component: A23P Front Side Door Latch-Passenger

Test 2

  1. Ignition/Vehicle - Off
  2. Disconnect the electrical connector: A23RR Rear Side Door Latch-Right
  3. Connect a test lamp between the test points: Control circuit terminal 8 & ground
  4. Ignition - On/Vehicle - In Service Mode
  5. Operate the component: S13D Door Lock Switch - Driver

    Verify the test lamp state:

    Not used = Test lamp Off

    Lock Switch - 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 2680 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 2680 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, ignition ON.
    2. Test for less than 1 V between the control 2680 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 
  6. Connect a test lamp between the test points: Control circuit terminal 9 & ground
  7. Ignition - On/Vehicle - In Service Mode
  8. Operate the component: S13D Door Lock Switch - Driver

    Verify the test lamp state:

    Not used = Test lamp Off

    Unlock - 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 1094 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 1094 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, ignition ON.
    2. Test for less than 1 V between the control 1094 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 
  9. Test or replace the component: A23RR Rear Side Door Latch-Right
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