LEMON Manuals: Even more car manuals for everyone
Home >> Cadillac >> 2021 >> CT4 Sport, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 87 (Lighting System - Diagnostic Information And Procedures (2 Of 2)) >> Diagnostic Information and Procedures >> Stop Lamps Malfunction >> 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.

Brake Pedal Position Sensor Malfunction

  1. Ignition OFF, disconnect the electrical connector at the B22 Brake Pedal Position Sensor, ignition ON.
  2. Verify a test lamp illuminates between the low reference circuit terminal 1 and B+.
    • If the test lamp does not illuminate 
    1. Test circuit 5360 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.
    • Go to next step: If the test lamp illuminates 
  3. Test for 4.8 - 5.2 V between 5 V reference circuit terminal 2 and ground.
    • If less than 4.8 V 
    1. Test circuit 5359 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. Test circuit 5359 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.
    3. Replace the K9 Body Control Module.
    • If greater than 5.2 V 
    1. Test circuit 5359 for a short to voltage.
      • If a short to voltage is found, repair the short to voltage 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 between 4.8 - 5.2 V 
  4. Test for less than 1 V between the signal circuit terminal 3 and ground.
    • If 1 V or greater 
    1. Test circuit 5361 for a short to voltage.
      • If a short to voltage is found, repair the short to voltage 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 less than 1 V 
    5. NOTE:

    The scan tool Brake Pedal Applied parameter will change to Active for 2 s as the 3 A fused jumper wire is connected between the 5 V reference circuit and the signal circuit and then default to Inactive. This is normal operation.

  5. Install a 3 A fused jumper wire between the 5 V reference terminal 2 and signal circuit terminal 3.
  6. Verify the scan tool Brake Pedal Applied parameter is Active for 2 s before defaulting to Inactive.
    • If not Active 
    1. Test circuit 5361 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. Test circuit 5361 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.
    3. Replace the K9 Body Control Module.
    • Go to next step: If Active 
  7. Replace the B22 Brake Pedal Position Sensor.

Stop Lamps Malfunction

  1. Ignition/vehicle off, disconnect the appropriate component:
    • E42L Rear Body Structure Stop Lamp - Left
    • E42R Rear Body Structure Stop Lamp - Right
  2. Verify a test lamp illuminates between the appropriate ground circuit terminal and B+:
    • E42L Rear Body Structure Stop Lamp - Left = Terminal 6
    • E42R Rear Body Structure Stop Lamp - Right = Terminal 1
    • If the test lamp does not illuminate 
    1. Repair the open/high resistance on the ground circuit or ground connection.
    • Go to next step: If the test lamp illuminates 
  3. Connect a test lamp between the appropriate control circuit terminal and ground, ignition on/vehicle in service mode:
    • E42L Rear Body Structure Stop Lamp - Left = Terminal 4
    • E42R Rear Body Structure Stop Lamp - Right = Terminal 3
  4. Verify the test lamp turns on and off when commanding the appropriate Turn Signal/Stop Lamp ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Test the appropriate circuit for a short to ground:
      • E42L Rear Body Structure Stop Lamp - Left = Circuit 1334
      • E42R Rear Body Structure Stop Lamp - Right = Circuit 1335
      • 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. Test the appropriate circuit for an open/high resistance:
      • E42L Rear Body Structure Stop Lamp - Left = Circuit 1334
      • E42R Rear Body Structure Stop Lamp - Right = Circuit 1335
      • 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
    3. Replace the K219 Lighting Control Module.
    • If the test lamp is always ON 
    1. Test the appropriate circuit for a short to voltage:
      • E42L Rear Body Structure Stop Lamp - Left = Circuit 1334
      • E42R Rear Body Structure Stop Lamp - Right = Circuit 1335
      • 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 K219 Lighting Control Module.
    • Go to next step: If the test lamp turns ON and OFF 
  5. Replace the appropriate lamp assembly.

Center High Mounted Stop Lamp Malfunction

  1. Ignition/vehicle off, disconnect the E6 High Mount Stop 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 the ground circuit or ground connection.
    • Go to next step: If the test lamp illuminates 
  3. Connect a test lamp between control circuit terminal 2 and ground, ignition on/vehicle in service mode.
  4. Verify the test lamp turns on and off when commanding the Center Stop Lamp ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Test circuit 820 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. Test circuit 820 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.
    3. Replace the K219 Lighting Control Module.
    • If the test lamp is always ON 
    1. Test circuit 820 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 K219 Lighting Control Module.
    • Go to next step: If the test lamp turns ON and OFF 
  5. Replace the E6 High Mount Stop Lamp.
scientia non olet · About LEMON Manuals