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Home >> Cadillac >> 2021 >> CT4 Sport, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 224 (Lighting System - Diagnostic Information And Procedures (1 Of 2)) >> Diagnostic Information and Procedures >> DTC B1837 >> 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.
  1. Set the S36 Dimmer Switch to full intensity.
  2. Ignition OFF, disconnect the X3 and X5 connector at the K9 Body Control Module, ignition ON:
  3. 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 
  4. Connect a 3 A fused jumper wire between B+ and control circuit terminal:
    • Connector X3 - terminal 4
    • Connector X5 - terminal 6
  5. 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
      • S13RR Door Lock Switch - Right Rear - 2450
      • K94RR Door Switch Panel Control Module - Right Rear - 2450
      • 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 
  6. Replace the K9 Body Control Module.
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