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Home >> GMC >> 2018 >> Acadia Denali, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 271 (Lighting System - DTC B0655 To DTC B3890) >> Diagnostic Information and Procedures >> DTC B3884: Center High Mounted Stop Lamp >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2017 Cadillac ATS. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, exterior lamps OFF, disconnect the harness connectors at the components listed below.
    • E6 Center High Mounted Stop Lamp
    • E42L Tail Lamp Assembly - Left (with TVN)
    • E42R Tail Lamp Assembly - Right (with TVN)
    • K68 Trailer Lighting Control Module X1 (with TVN/V2S)
  2. Test for less than 5 Ω between the appropriate ground circuit terminal listed below and ground.
    • E6 Center High Mounted Stop Lamp terminal 2 (Coupe)
    • E6 Center High Mounted Stop Lamp terminal B (Sedan)
    • E42L Tail Lamp Assembly - Left terminal A (with TVN)
    • E42R Tail Lamp Assembly - Right terminal E (with TVN)
    • If 5 Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
    • If less than 5 Ω 
  3. Connect a test lamp between the appropriate control circuit terminal listed below and ground, ignition ON.
    • E6 Center High Mounted Stop Lamp terminal 1 (Coupe)
    • E6 Center High Mounted Stop Lamp terminal A (Sedan)
    • E42L Tail Lamp Assembly - Left terminal C (with TVN)
    • E42R Tail Lamp Assembly - Right terminal C (with TVN)
    • K68 Trailer Lighting Control Module terminal 14 X1 (with TVN/V2S)
  4. Verify the test lamp turns ON and OFF when commanding the Stop Lamps (with TVN) or Center Brake Lamp (without TVN) ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the appropriate harness connector listed below at the K9 Body Control Module.
      • X4 - without TVN
      • X6 - with TVN
    2. Test for infinite resistance between the control circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in the control circuit 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, disconnect the appropriate harness connector listed below at the K9 Body Control Module, ignition ON.
      • X4 - without TVN
      • X6 - with TVN
    2. Test for less than 1 V between the control circuit terminal 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.
    • If the test lamp turns ON and OFF 
  5. Test or replace the inoperative component.
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