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Home >> Cadillac >> 2018 >> Escalade ESV Platinum, RWD >> Repair and Diagnosis >> Accessories & Equipment >> Interior/Illumination Lights >> Lighting System - DTC B0655 To DTC B3951 >> Diagnostic Information And Procedures >> DTC B3950 Or B3951: Left/Right Rear Turn Signal Circuit >> Circuit/System Testing

Circuit/System Testing

DTC B3950

  1. Ignition OFF, exterior lamps OFF, All doors closed, open and close drivers door, disconnect the appropriate component listed below. It may take up to 2 min for all vehicle systems to power down.
    • E4LR Turn Signal Lamp - Left Rear (X88 with T89)
    • E42L Tail Lamp Assembly - Left (Z75/Z88)
    • E5AS Stop/Turn Signal Lamp - Left Upper (X88 without T89)
    • E5AT Stop/Turn Signal Lamp - Left Lower (X88 without T89)
  2. Test for less than 15 Ω between the appropriate ground circuit terminal listed below and ground.
    • E4LR Turn Signal Lamp - Left Rear socket terminal (X88 with T89)
    • E42L Tail Lamp Assembly - Left terminal 6 (Z75/Z88)
    • E5AS Stop/Turn Signal Lamp - Left Upper socket terminal (X88 without T89)
    • E5AT Stop/Turn Signal Lamp - Left Lower socket terminal (X88 without T89)
    • If 15 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.
    • Go to next step: If less than 15 Ω 
  3. Connect a test lamp between the appropriate control circuit terminal listed below and ground, ignition ON.
    • E4LR Turn Signal Lamp - Left Rear socket terminal (X88 with T89)
    • E42L Tail Lamp Assembly - Left terminal 2 (Z75/Z88)
    • E5AS Stop/Turn Signal Lamp - Left Upper socket terminal (X88 without T89)
    • E5AT Stop/Turn Signal Lamp - Left Lower socket terminal (X88 without T89)
  4. Verify the test lamp turns ON and OFF when commanding the Left Rear Turn Signal/Stop Lamp ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the X5 harness connector at the K9 Body Control Module.
    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 X5 harness connector at the K9 Body Control Module, ignition ON.
    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.
    • Go to next step: If the test lamp turns ON and OFF 
  5. Replace the appropriate turn signal lamp - left rear.

DTC B3951

  1. Ignition OFF, exterior lamps OFF, All doors closed, open and close drivers door, disconnect the appropriate component listed below. It may take up to 2 min for all vehicle systems to power down.
    • E4RR Turn Signal Lamp - Right Rear (X88 with T89)
    • E42R Tail Lamp Assembly - Right (Z75/Z88)
    • E5AU Stop/Turn Signal Lamp - Right Upper (X88 without T89)
    • E5AV Stop/Turn Signal Lamp - Right Lower (X88 without T89)
  2. Test for less than 15 Ω between the appropriate ground circuit terminal listed below and ground.
    • E4RR Turn Signal Lamp - Right Rear socket terminal (X88 with T89)
    • E42R Tail Lamp Assembly - Right terminal 6 (Z75/Z88)
    • E5AU Stop/Turn Signal Lamp - Right Upper socket terminal (X88 without T89)
    • E4AV Stop/Turn Signal Lamp - Right Lower socket terminal (X88 without T89)
    • If 15 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.
    • Go to next step: If less than 15 Ω 
  3. Connect a test lamp between the appropriate control circuit terminal listed below and ground, ignition ON.
    • E4RR Turn Signal Lamp - Right Rear socket terminal (X88 with T89)
    • E42R Tail Lamp Assembly - Right terminal 2 (Z75/Z88)
    • E5AU Stop/Turn Signal Lamp - Right Upper socket terminal (X88 without T89)
    • E4AV Stop/Turn Signal Lamp - Right Lower socket terminal (X88 without T89)
  4. Verify the test lamp turns ON and OFF when commanding the Right Rear Turn Signal/Stop Lamp ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the X4 harness connector at the K9 Body Control Module.
    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 X4 harness connector at the K9 Body Control Module, ignition ON.
    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.
    • Go to next step: If the test lamp turns ON and OFF 
  5. Replace the appropriate stop/turn signal lamp - right rear.
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