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Circuit/System Testing

Headlamp Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the S30 headlamp switch.
  2. Ignition OFF, test for less than 30 Ω between the ground circuit terminal 6 and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Headlamps On Switch parameter is Inactive.
    • If not the specified value, test the signal circuit terminal 4 for short to ground. If the circuit tests normal, replace the K9 BCM.
  4. Verify the scan tool Automatic Headlamps Disable Switch parameter is Inactive.
    • If not the specified value, test the signal circuit terminal 5 for short to ground. If the circuit tests normal, replace the K9 BCM.
  5. Install a 3 A fused jumper wire between the signal circuit terminal 4 and ground. Verify the scan tool Headlamps On Switch parameter is Active.
    • If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
  6. Install a 3 A fused jumper wire between the signal circuit terminal 5 and ground. Verify the scan tool Automatic Headlamps Disable Switch parameter is Active.
    • If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
  7. If all circuits test normal, test or replace the S30 headlamp switch.

Turn Signal/Multifunction Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the S78 turn signal/multifunction switch.
  2. Ignition OFF, test for less than 5.0 Ω between the ground circuit terminal 3 and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Headlamps Flash Switch parameter is Inactive.
    • If not the specified value, test the signal circuit terminal 4 for a short to ground. If the circuit tests normal, replace the K9 BCM.
  4. Verify the scan tool High Beam Select Switch parameter is Inactive.
    • If not the specified value, test the signal circuit terminal 2 for a short to ground. If the circuit tests normal, replace the K9 BCM.
  5. Install a 3 A fused jumper wire between the signal circuit terminal 4 and ground. Verify the scan tool Headlamps Flash Switch parameter is Active.
    • If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
  6. Install a 3 A fused jumper wire between the signal circuit terminal 2 and ground. Verify the scan tool High Beam Select Switch parameter is Active.
    • If not the specified value, test the signal circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the K9 BCM.
  7. If all circuits test normal, test or replace the S78 turn signal/multifunction switch.

Headlamps Malfunction - Low Beam

  1. Ignition OFF, disconnect the harness connector at the appropriate E13 headlamp.
  2. Ignition OFF, scan tool disconnected, exterior lamps OFF, test for less than 5.0 Ω between the ground circuit terminal 1 and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the control circuit terminal 3 and ground.
  4. Command the appropriate Headlamp Low Beam ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K9 BCM.
    • If the test lamp is always OFF, test the control circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the K9 BCM.
  5. If all circuits test normal, test or replace the E13 headlamp.

High Beam Headlamps Inoperative

  1. Ignition OFF, disconnect the harness connector at the appropriate E4 Headlamp - High Beam.
  2. Test for less than 30 Ω between the ground circuit terminal 2 and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the control circuit terminal 1 and ground.
  4. Ignition ON, command the High Beams ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the X50A underhood fuse block.
    • If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the X50A underhood fuse block.
  5. If all circuits test normal, test or replace the bulb or the E4 Headlamp - High Beam

High Beam Command Malfunction

  1. Ignition OFF, disconnect the X2 harness connector at the X50A underhood fuse block.
  2. Connect a test lamp between the control circuit terminal 58 and B+.
  3. Ignition ON, command the High Beam Lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
    • If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the K9 BCM
  4. Ignition OFF, connect the X2 harness connector and disconnect the X1 harness connector at the X50A underhood fuse block.
  5. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminals listed below and ground.
    • Control terminal 13
    • Control terminal 14
    • If the test lamp is always ON, test the control circuit for a short to voltage.
  6. If all circuits test normal, replace the X50A underhood fuse block.
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