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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 B388B Or B388C: Secondary Left/Right Tail And Brake Lamp Circuit >> Circuit/System Testing

Circuit/System Testing

  1. Ignition OFF, exterior lamps OFF, disconnect the appropriate harness connector listed below.
    • E56L Rear Multifunction Carrier Tail Lamp Assembly - Left
    • E56R Rear Multifunction Carrier Tail Lamp Assembly - Right
  2. Test for less than 5 Ω between the appropriate ground circuit terminal listed below and ground.
    • E56L Rear Multifunction Carrier Tail Lamp Assembly - Left terminal C
    • E56R Rear Multifunction Carrier Tail Lamp Assembly - Right terminal B
    • 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.
    • Go to next step: If less than 5 Ω 
  3. Connect a test lamp between the appropriate control circuit terminal listed below and ground, ignition ON
    • E56L Rear Multifunction Carrier Tail Lamp Assembly - Left terminal B
    • E56R Rear Multifunction Carrier Tail Lamp Assembly - Right terminal C
  4. Verify the test lamp turns ON and OFF when commanding the appropriate Auxiliary Tail and Brake Lamp test with a scan tool.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the X1 harness connector at the K68 Trailer Lighting 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 K68 Trailer Lighting Control Module.
    • If the test lamp is always ON 
    1. Ignition OFF, disconnect the X1 harness connector at the K68 Trailer Lighting 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 K68 Trailer Lighting Control Module.
    • Go to next step: If the test lamp turns ON and OFF 
  5. Test or replace the E56 Rear Multifunction Carrier Tail Lamp Assembly.
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