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Home >> GMC >> 2018 >> Acadia Denali, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 274 (Lighting System - DTC B3891 To DTC C0297 And Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> Stop Lamps Malfunction >> 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.

Brake Pedal Position Sensor Malfunction

  1. Ignition OFF, disconnect the harness connector at the B22 Brake Pedal Position Sensor, ignition ON.
  2. Test for less than 1 V between the low reference circuit terminal 2 and ground.
    • If 1 V or greater 
    1. Ignition OFF, disconnect the X1 harness connector at the K9 Body Control Module, ignition ON.
    2. Test for less than 1 V between the low reference circuit 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 less than 1 V 
  3. Test or replace the B22 Brake Pedal Position Sensor.

Stop Lamps Malfunction

  1. Ignition OFF, exterior lamps OFF, disconnect the harness connectors at the appropriate E42 Tail Lamp Assembly. It may take up to 2 min for all vehicle systems to power down.
  2. Test for less than 5 Ω between the appropriate ground circuit terminal listed below and ground.
    • E42L Tail Lamp Assembly - Left terminal A
    • E42R Tail Lamp Assembly - Right terminal E
    • E42R Tail Lamp Assembly - Right terminal D (without 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.
    • E42L Tail Lamp Assembly - Left terminal C
    • E42R Tail Lamp Assembly - Right terminal C
    • E42R Tail Lamp Assembly - Right terminal B (without TVN)
  4. Verify the test lamp turns ON and OFF when commanding the Stop Lamps 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 - right tail lamp assembly (without TVN)
      • X5 - left tail lamp assembly (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 - right tail lamp assembly (without TVN)
      • X5 - left tail lamp assembly (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 E42 Tail Lamp Assembly.

Center High Mount Stop Lamp Malfunction

  1. Ignition OFF, exterior lamps OFF, disconnect the harness connectors at the components listed below. It may take up to 2 min for all vehicle systems to power down.
    • 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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