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Home >> Chevrolet >> 2019 >> Suburban 3500 HD LS >> Repair and Diagnosis >> Accessories & Equipment >> Exterior Lights >> Lighting System - Diagnostic Information And Procedures (DTC B3950-C0297) >> Diagnostic Information and Procedures >> Front Fog Lamps Malfunction >> Circuit/System Testing

Circuit/System Testing

Front Fog Lamp Switch Malfunction

  1. Ignition OFF, scan tool disconnected, all doors closed, all accessories OFF, disconnect the harness connector at the S30 Headlamp Switch. 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 8 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 the scan tool Front Fog Lamps Switch parameter is Inactive.
    • If not Inactive 
    1. Ignition OFF, disconnect the X1 harness connector at the K9 Body Control Module.
    2. Test for infinite resistance between the signal circuit terminal 10 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 Inactive 
  5. Install a 3 A fused jumper wire between the signal circuit terminal 10 and ground.
  6. Verify the scan tool Front Fog Lamps Switch parameter is Active.
    • If not Active 
    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 signal circuit terminal 10 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 Active 
  7. Test or replace the S30 Headlamp Switch.

Front Fog Lamps Malfunction

  1. Ignition OFF, disconnect the X5 harness connector at the K9 Body Control Module, ignition ON.
  2. Verify a test lamp illuminates between the control circuit terminal 10 and ground.
    • If the test lamp does not illuminate 
    1. Ignition OFF, disconnect the X3 harness connector at the X50A Fuse Block - Underhood.
    2. Test for infinite resistance between the control circuit terminal 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 X50A Fuse Block - Underhood.
    • Go to next step: If the test lamp illuminates 
  3. Ignition OFF, remove the F94UA fog lamp fuse at the X50A Fuse Block - Underhood.
  4. Connect a 3 A fused jumper between the control circuit terminal 10 and ground, ignition ON.
  5. Verify a test lamp illuminates between the F94UA fog lamp fuse B+ switch control terminal and ground.
    • If the test lamp does not illuminate 
    1. Ignition OFF, disconnect the X3 harness connector at the X50A Fuse Block - Underhood, ignition ON.
    2. Test for less than 1 V between the control circuit terminal 10 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the X50A Fuse Block - Underhood.
    • Go to next step: If the test lamp illuminates 
  6. Ignition OFF, connect the X5 harness connector at the K9 Body Control Module.
  7. Install the F94UA fog lamp fuse at the X50A Fuse Block - Underhood.
  8. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the appropriate E29 Fog Lamp. It may take up to 2 min for all vehicle systems to power down.
  9. Test for less than 10 Ω between the ground circuit terminal B and ground.
    • If 10 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 10 Ω 
  10. Connect a test lamp between the control circuit terminal A and ground, ignition ON.
  11. Verify the test lamp turns ON and OFF when commanding the Front Fog Lamps ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the X1 harness connector at the X50A Fuse Block - Underhood.
    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 X1 harness connector at the X50A Fuse Block - Underhood, 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 
  12. Test or replace the E29 Fog Lamp.
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