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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 >> Interior Backlighting 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.

Dimmer Switch Malfunction

  1. Ignition OFF, disconnect the connector at the S36 Dimmer Switch, ignition ON.
  2. Verify a test lamp illuminates between low reference terminal 1 and B+.
    • If the test lamp does not illuminate 
    1. Test circuit 5005 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 V - 5.2 V between signal circuit terminal 2 and ground.
    • If less than 4.8 V 
    1. Test circuit 44 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 44 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 44 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 4.8 V - 5.2 V 
  4. Replace the S36 Dimmer Switch.

Interior Backlighting Malfunction

    NOTE:

    Circuit/System Verification must be performed before Circuit/System Testing.

    Each component with backlighting may need to be disconnected to isolate a short to voltage or short to ground. Use the schematics to identify the following:

    • Backlighting components the vehicle is equipped with
    • Each component's control and ground circuit terminals
    • Component locations on the backlighting control circuit
  1. Ignition OFF, disconnect the connector at the component with inoperative backlighting.
  2. Headlamps ON, set the S36 Dimmer Switch to full intensity.
  3. Ignition OFF, disconnect the X3 and X5 connector at the K9 Body Control Module, ignition ON:
  4. Verify the appropriate accent/courtesy lamps are not illuminated:
    • S36 Dimmer Switch
    • S38 On/Off Vehicle Switch
    • S27 Head - Up Display Switch
    • S26 Hazard Warning Switch
    • S86 Vehicle Stability Control System Switch
    • X92C Single Charge Only 2nd Row Receptacle - Floor Console Rear
    • X80G Accessory Power Receptacle - Instrument Panel
    • X82 Audio/Video Input Adapter
    • S25 Garage Door Opener Transmitter
    • S13LR Door Lock Switch - Left Rear
    • K94LR Door Switch Panel Control Module - Left Rear
    • S13RR Door Lock Switch - Right Rear
    • K94RR Door Switch Panel Control Module - Right Rear
    • If an accent/courtesy lamp is illuminated 

      Repair the short to voltage on circuit 6817.

    • Go to next step: If all accent/courtesy lamp are not illuminated 
  5. Connect a 3 A fused jumper wire between B+ and appropriate control circuit terminal:
    • Connector X3 - terminal 4
    • Connector X5 - terminal 6
  6. Verify the appropriate accent/courtesy lamps are illuminated.
    • If the accent/courtesy lamp is not illuminated and the jumper fuse is OK. 
    1. Test the appropriate circuit for an open/high resistance:
      • S36 Dimmer Switch - 1350
      • S38 On/Off Vehicle Switch - 1351
      • S27 Head - Up Display Switch - 1350
      • S26 Hazard Warning Switch - 1450
      • S86 Vehicle Stability Control System Switch - 1450
      • X92C Single Charge Only 2nd Row Receptacle - Floor Console Rear - 1450
      • X80G Accessory Power Receptacle - Instrument Panel - 1450
      • X82 Audio/Video Input Adapter - 2851
      • S25 Garage Door Opener Transmitter - 2350
      • S13LR Door Lock Switch - Left Rear - 2350
      • K94LR Door Switch Panel Control Module - Left Rear - 2350
      • If an open/high resistance is found, repair the fault on the circuit or ground connection.
      • Go to next step: If an open/high resistance is not found.
    2. Test circuit 6817 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 appropriate accent/courtesy lamp.
    • If the accent/courtesy lamp is not illuminated and the jumper fuse is open 
    1. Test circuit 6817 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 appropriate accent/courtesy lamp.
    • Go to next step: If the accent/courtesy lamp is illuminated 
  7. Replace the K9 Body Control Module.

Switch LED Indicator Malfunction

    NOTE:

    Circuit/System Verification must be performed before Circuit/System Testing.

    Each switch with a LED indicator may need to be disconnected to isolate a short to voltage or short to ground. Use the schematics to identify the following:

    • LED indicators the vehicle is equipped with
    • Each component's LED indicator control and ground circuit terminals
    • Component locations on the LED indicator control circuit
  1. Ignition OFF, disconnect the connector at the component with the inoperative LED indicator:
    • S47D Seat Memory Switch - Driver
    • S13D Door Lock Switch - Driver
    • S58B Rear Compartment Lid Unlatch Switch - Interior
    • S13P Door Lock Switch - Passenger
    • S70L Steering Wheel Controls Switch - Left
  2. Connect a test lamp between the appropriate LED indicator control circuit terminal and ground, ignition ON:
    • S47D Seat Memory Switch - Driver - terminal 1
    • S13D Door Lock Switch - Driver - terminal 1
    • S58B Rear Compartment Lid Unlatch Switch - Interior - terminal 1
    • S13P Door Lock Switch - Passenger - terminal 1
    • S70L Steering Wheel Controls Switch - Left - terminal 2
  3. Verify the test lamp illuminates and changes intensity while adjusting the S36 Dimmer Switch from high to low intensity.
    • If the test lamp does not illuminate 
    1. Test the appropriate circuit for an open/high resistance:
      • S47D Seat Memory Switch - Driver - 2150
      • S13D Door Lock Switch - Driver - 2150
      • S58B Rear Compartment Lid Unlatch Switch - Interior - 2150
      • S13P Door Lock Switch - Passenger - 2250
      • S70L Steering Wheel Controls Switch - Left - 1351
      • If an open/high resistance is found, repair the fault on the circuit or ground connection.
      • Go to next step: If an open/high resistance is not found.
    2. Test the appropriate circuit for a short to ground:
      • S47D Seat Memory Switch - Driver - 4784
      • S13D Door Lock Switch - Driver - 4784
      • S58B Rear Compartment Lid Unlatch Switch - Interior - 4784
      • S13P Door Lock Switch - Passenger - 4638
      • S70L Steering Wheel Controls Switch - Left - 3893
      • 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.
    3. Test circuit the appropriate circuit for an open/high resistance.
      • S47D Seat Memory Switch - Driver - 4784
      • S13D Door Lock Switch - Driver - 4784
      • S58B Rear Compartment Lid Unlatch Switch - Interior - 4784
      • S13P Door Lock Switch - Passenger - 4638
      • S70L Steering Wheel Controls Switch - Left - 3893
      • 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.
    4. Replace the appropriate module:
      • S47D Seat Memory Switch - Driver - S84D Door Switch Panel Control Module - Driver
      • S13D Door Lock Switch - Driver - S84D Door Switch Panel Control Module - Driver
      • S58B Rear Compartment Lid Unlatch Switch - Interior - S84D Door Switch Panel Control Module - Driver
      • S13P Door Lock Switch - Passenger - S84P Door Switch Panel Control Module - Passenger
      • S70L Steering Wheel Controls Switch - Left - S70R Steering Wheel Controls Switch - Right
    • If the test lamp illuminates but does not change intensity 
    1. Test the appropriate circuit for a short to voltage:
      • S47D Seat Memory Switch - Driver - 4784
      • S13D Door Lock Switch - Driver - 4784
      • S58B Rear Compartment Lid Unlatch Switch - Interior - 4784
      • S13P Door Lock Switch - Passenger - 4638
      • S70L Steering Wheel Controls Switch - Left - 3893
      • 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 appropriate module:
      • S47D Seat Memory Switch - Driver - S84D Door Switch Panel Control Module - Driver
      • S13D Door Lock Switch - Driver - S84D Door Switch Panel Control Module - Driver
      • S58B Rear Compartment Lid Unlatch Switch - Interior - S84D Door Switch Panel Control Module - Driver
      • S13P Door Lock Switch - Passenger - 4638 - S84P Door Switch Panel Control Module - Passenger
      • S70L Steering Wheel Controls Switch - Left - S70R Steering Wheel Controls Switch - Right
    • Go to next step: If the test lamp illuminates and changes intensity 
  4. Replace the appropriate component:
    • S47D Seat Memory Switch - Driver
    • S13D Door Lock Switch - Driver
    • S58B Rear Compartment Lid Unlatch Switch - Interior
    • S13P Door Lock Switch - Passenger
    • S70L Steering Wheel Controls Switch - Left
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