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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 981 (Lighting Systems) >> Diagnostic Information and Procedures >> Turn Signal Lamps and/or Indicators Malfunction >> Circuit/System Testing

Circuit/System Testing

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Turn Signal Lamp Circuit Malfunction

  1. Ignition OFF, disconnect the X4 harness connector at the BCM.
  2. Ignition ON, verify a test lamp illuminates between the following B+ terminals and ground.
    • B+ terminal 1
    • B+ terminal 2
    • B+ terminal 3
    • If the test lamp does not illuminate, test the B+ circuit for an open/high resistance. If the circuit fuse is open, test the B+ circuit and the affected turn signal control circuits for a short to ground.
  3. Ignition OFF, connect the harness connector X4 harness connector at the BCM.
  4. Disconnect the harness connector at the affected turn signal lamp.
  5. Test for less than 1.0 ohms of resistance between the affected ground circuit terminal and ground.
    • Front terminal G
    • Rear terminal GRD
    • Outside mirror terminal 10
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  6. Connect a test lamp between the affected turn signal control circuit terminal and ground.
    • Front terminal MIN
    • Rear terminal MJR
    • Outside mirror terminal 5
  7. Ignition ON, command the affected 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 supply voltage circuit for a short to voltage. If the circuit tests normal, replace the BCM.
    • If the test lamp is always off, test the supply voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  8. If all circuits test normal, test or replace the appropriate turn signal bulb.

Turn Signal Switch Circuit Test

  1. Ignition OFF, disconnect the harness connector 1 at the turn signal/multifunction switch.
  2. Test for less than 1.0 ohm of resistance between the ground circuit terminal F and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool left and right turn signal parameters are Inactive.
    • If not the specified value, test the affected signal circuit terminal for a short to ground. If the circuit tests normal, replace the BCM.
      • Left terminal E
      • Right terminal D
  4. Install a 3A fused jumper wire between the affected signal circuit terminal and the ground circuit terminal F. Verify the scan tool left or right turn signal parameter is Active.
    • Left terminal E
    • Right terminal D
    • If not the specified value, test the affected signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
  5. If all circuits test normal, test or replace the turn signal/multifunction switch.
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