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Circuit/System Testing: Notes

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Turn Signal Lamp Malfunction

  1. Ignition OFF, disconnect the X4 harness connector at the BCM.
  2. Verify that a test lamp illuminates between the LT STOP TRN fuse B+ circuit terminal 1 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  3. Verify that a test lamp illuminates between the RT STOP TRN fuse B+ circuit terminal 3 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  4. Ignition OFF, reconnect the X4 harness connector at the BCM.
  5. Disconnect the harness connector at the appropriate turn signal lamp.
  6. Test for less than 5.0 ohms between the appropriate ground circuit terminal and ground.
    • Park/Turn Signal Lamp - Left front terminal C - with X88/Z88
    • Park/Turn Signal Lamp - Right front terminal A - with X88/Z88
    • Turn Signal Lamp - Left and Right front terminal 3- with Z75
    • Repeater Lamp - Left and Right front terminal 2 - with TR2
    • Tail/Turn Signal Lamp - Left and Right rear terminal GRD - with X88
    • Tail/Turn Signal Lamp - Left and Right rear terminal G- w/o X88
    • Tail/Stop and Turn Signal Lamp - Left and Right Upper rear terminal GRD - with X88/Z75 - EXP - E52
    • Tail/Stop and Turn Signal Lamp - Left and Right Lower rear terminal GRD - with X88/Z75 - EXP - E52
    • Tail Lamp Circuit Board - Left and Right rear terminal D - with Z75 + E52
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Connect a test lamp between the appropriate turn signal control circuit terminal and ground.
    • Park/Turn Signal Lamp - Left front terminal A - with X88/Z88
    • Park/Turn Signal Lamp - Right front terminal D - with X88/Z88
    • Turn Signal Lamp - Left and Right front terminal 1- with Z75
    • Repeater Lamp - Left and Right front terminal 1- with TR2
    • Tail/Turn Signal Lamp - Left and Right rear terminal MJR - with X88
    • Tail/Turn Signal Lamp - Left and Right rear terminal A - w/o X88
    • Tail/Stop and Turn Signal Lamp - Left and Right Upper rear terminal MJR - with X88/Z75 - EXP - E52
    • Tail/Stop and Turn Signal Lamp - Left and Right Lower rear terminal MJR - with X88/Z75 - EXP - E52
    • Tail Lamp Circuit Board - Left and Right rear terminal B - with Z75 + E52 - with EXP
    • Tail Lamp Circuit Board - Left and Right rear terminal E - with Z75 + E52 - w/o EXP
  8. Ignition ON, command the appropriate turn signal 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 BCM.
    • 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 BCM.
  9. If all circuits test normal, test or replace the appropriate turn signal lamp.

Turn Signal Switch Malfunction

  1. Ignition OFF, disconnect the harness connector X1 at the turn signal/multifunction switch.
  2. Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal F.
    • If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Left Front and Rear Turn Signal Switch parameter is INACTIVE.
    • If not the specified value, test the signal circuit terminal E for a short to ground. If the circuit tests normal, replace the BCM.
  4. Verify the scan tool Right Front and Rear Turn Signal Switch parameter is INACTIVE.
    • If not the specified value, test the signal circuit terminal D for a short to ground. If the circuit tests normal, replace the BCM.
  5. Verify the scan tool Hazard Lamp Switch parameter is INACTIVE.
    • If not the specified value, test the signal circuit terminal G for a short to ground. If the circuit tests normal, replace the BCM.
  6. Install a 3A fused jumper wire between the signal circuit terminal E and ground. Verify the scan tool Left Turn Signal 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 BCM.
  7. Install a 3A fused jumper wire between the signal circuit terminal D and ground. Verify the scan tool Right Turn Signal 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 BCM.
  8. Install a 3A fused jumper wire between the signal circuit terminal G and ground. Verify the scan tool Hazard Lamp 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 BCM.
  9. If all circuits test normal, test or replace the turn signal/multifunction switch.
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