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Home >> Cadillac >> 2018 >> XT5 Platinum >> Repair and Diagnosis >> Accessories & Equipment >> Headlights >> Lighting System - Diagnostic Information And Procedures (DTC B3950 - C0297) >> Diagnostic Information and Procedures >> Daytime Running Lamps Malfunction >> Circuit/System Testing

Circuit/System Testing

Daytime Running Lamps Malfunction (with T4A)

  1. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the appropriate E13 Headlamp Assembly. It may take up to 2 min for all vehicle systems to power down.
  2. Test for less than 5 Ω between the ground circuit terminal 4 and ground.
    • 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 control circuit terminal 7 and ground, ignition ON.
  4. Verify the test lamp turns ON and OFF when commanding the appropriate Dedicated Daytime Running Lamp 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 - left daytime running lamp
      • X5 - right daytime running lamp
    2. Test for infinite resistance between the control circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • Go to next step: 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 - left daytime running lamp
      • X5 - right daytime running lamp
    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. Test or replace the E13 Headlamp Assembly.

Daytime Running Lamps Malfunction (with T4L)

  1. Ignition OFF, disconnect the KR50 Headlamp Relay.
  2. Verify a test lamp illuminates between the B+ circuit terminal 85 and ground.
    • If the test lamp does not illuminate 

      Replace the X50A Fuse Block - Underhood.

    • Go to next step: If the test lamp illuminates 
  3. Verify a test lamp illuminates between the B+ circuit terminal 30 and ground.
    • If the test lamp does not illuminate 

      Replace the X50A Fuse Block - Underhood.

    • Go to next step: If the test lamp illuminates 
  4. Connect a test lamp between the control circuit terminal 86 and B+, ignition ON.
  5. Verify the test lamp turns ON and OFF when commanding the headlamps ON and OFF with the S78 Turn Signal/Multifunction Switch.
    • If the test lamp is always OFF 
    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 13 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • Go to next step: If less than 1 V
    3. Ignition OFF.
    4. 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.
    2. Test for infinite resistance between the control circuit terminal 13 and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the K9 Body Control Module.
    • Go to next step: If the test lamp turns ON and OFF 
  6. Ignition OFF, connect the KR50 Headlamp Relay.
  7. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the appropriate E13 Headlamp Assembly. It may take up to 2 min for all vehicle systems to power down.
  8. Test for less than 5 Ω between the ground circuit terminal 4 and ground.
    • 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 
  9. Connect a test lamp between the control circuit terminal 5 and ground, ignition ON.
  10. Verify the test lamp turns ON and OFF when commanding the headlamps ON and OFF with the S78 Turn Signal/Multifunction Switch.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the X5 harness connector at the X50A Fuse Block - Underhood.
    2. Test for infinite resistance between the control circuit terminal 5 and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • Go to next step: 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 KR50 Headlamp Relay.
    • If the test lamp is always ON 
    1. Ignition OFF, disconnect the X5 harness connector at the X50A Fuse Block - Underhood, ignition ON.
    2. Test for less than 1 V between the control circuit terminal 5 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the KR50 Headlamp Relay.
    • Go to next step: If the test lamp turns ON and OFF 
  11. Ignition OFF.
  12. Connect a test lamp between the control circuit terminal 7 and ground, ignition ON.
  13. Verify the test lamp turns ON and OFF when commanding the appropriate Dedicated Daytime Running Lamp 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 - left daytime running lamp
      • X5 - right daytime running lamp
    2. Test for infinite resistance between the control circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • Go to next step: 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 - left daytime running lamp
      • X5 - right daytime running lamp
    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 
  14. Test or replace the E13 Headlamp Assembly.

Ambient Light Sensor Malfunction - (without CE1)

  1. Ignition OFF, scan tool disconnected, all doors closed, all accessories OFF, open and close drivers door, disconnect the harness connector at the B10B Ambient Light/Sunload Sensor. It may take up to 10 min for all vehicle systems to power down.
  2. Test for less than 10 Ω between the low reference circuit terminal 6 and ground.
    • If 10 Ω or greater 
    1. Ignition OFF, disconnect the X2 harness connector at the K33 HVAC Control Module.
    2. Test for less than 2 Ω in the low reference circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K33 HVAC Control Module.
    • Go to next step: If less than 10 Ω 
  3. Ignition ON.
  4. Verify the scan tool Ambient Light Sensor parameter is greater than 4.65 V.
    • If 4.65 V or less 
    1. Ignition OFF, disconnect the X2 harness connector at the K9 Body Control Module.
    2. Test for infinite resistance between the signal circuit terminal 3 and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the K9 Body Control Module.
    • Go to next step: If greater than 4.65 V 
  5. Install a 3 A fused jumper wire between the signal circuit terminal 3 and the low reference circuit terminal 6.
  6. Verify the scan tool Ambient Light Sensor parameter is less than 0.196 V.
    • If 0.196 V or greater 
    1. Ignition OFF, disconnect the X2 harness connector at the K9 Body Control Module, ignition ON.
    2. Test for less than 1 V between the signal circuit terminal 3 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • Go to next step: If less than 1 V
    3. Test for less than 2 Ω in the signal 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.
    • Go to next step: If less than 0.196 V 
  7. Test or replace the B10B Ambient Light/Sunload Sensor.

Rain/Ambient Light Sensor Module Malfunction - (with CE1)

  1. Ignition OFF, scan tool disconnected, all doors closed, all accessories OFF, disconnect the harness connector at the B200 Rain Sensor Module. It may take up to 2 min for all vehicle systems to power down.
  2. Test for less than 15 Ω between the ground circuit terminal 3 and ground.
    • 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. Ignition ON.
  4. Verify a test lamp illuminates between the B+ circuit terminal 1 and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Ignition OFF, disconnect the X2 harness connector at the X53A Fuse Block - Rear Body.
    2. Test for less than 2 Ω in the B+ circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.
    • If the test lamp does not illuminate and the circuit fuse is open 
    1. Ignition OFF, disconnect the X2 harness connector at the X53A Fuse Block - Rear Body.
    2. Test for infinite resistance between the B+ circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the X53A Fuse Block - Rear Body.
    • Go to next step: If the test lamp illuminates 
  5. Test or replace the B200 Rain Sensor Module.
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