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Circuit/System Testing

WARNING: This page is about a different car, the 2007 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.

Stop Lamps Circuit Test -- Domestic

  1. Ignition OFF, disconnect the (C4) harness connector at the BCM.
  2. Ignition ON, verify a test lamp illuminates between the terminals listed below and ground.
    • B+ terminal 1
    • B+ terminal 3
    • B+ terminal 4
    • 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 respective stop lamp circuits for a short to ground.
  3. Ignition OFF, disconnect the harness connector at the brake pedal position sensor.
  4. Verify that a test lamp illuminates between the low reference circuit terminal C and B+.
    • 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 BCM.
  5. Ignition OFF, disconnect harness connector at the inoperative stop/turn lamp.
  6. Ignition OFF, test for less than 5.0 ohms of resistance between the ground circuit terminal C and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Connect a test lamp between the supply voltage circuit terminal B and ground.
  8. Ignition ON, command the appropriate LR or RR 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.
  9. If all circuits test normal, replace the inoperative stop/turn signal bulb or lamp assembly.

Stop Lamps Circuit Test -- Export

  1. Ignition OFF, disconnect the (C4) harness connector at the BCM.
  2. Ignition ON, verify a test lamp illuminates between the B+ terminals listed below and ground.
    • B+ terminal 1
    • B+ terminal 3
    • B+ terminal 4
    • 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 respective stop lamp circuits for a short to ground.
  3. Ignition OFF, disconnect the harness connector at the brake pedal position sensor.
  4. Verify that a test lamp illuminates between the low reference circuit terminal C and B+.
    • 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 BCM.
  5. Ignition OFF, disconnect the STOP LAMP EXP Relay from the rear fuse block.
  6. Test for less than 5 ohms of resistance between the ground circuit terminal 9 and ground
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Ignition ON, verify a test lamp does not illuminate between the supply voltage terminal 6 and ground.
    • If the test lamp illuminates, test the supply voltage circuit for a short to voltage.
  8. Verify that a test lamp illuminates between the B+ circuit terminal 10 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  9. Connect a test lamp between the supply voltage circuit terminal 8 and the ground circuit terminal 9.
  10. Ignition ON, apply and release the brake pedal. The test lamp should turn ON and OFF as the brake pedal is applied and released.
    • 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.
  11. Disconnect the harness connector at the inoperative stop lamp.
  12. Ignition OFF, test for less than 5.0 ohms of resistance between the ground circuit terminal H and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  13. Connect a test lamp between the supply voltage circuit terminal B and ground.
  14. Connect a 3A fused jumper wire between the stop lamp relay B+ circuit terminal 10 and the supply voltage circuit terminal 6. The test lamp should illuminate.
    • If the test lamp does not illuminate, test the supply voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the bulb.
  15. If all circuits test normal, test or replace the stop lamp relay.

High Mounted Stop Lamp Malfunction

  1. Ignition OFF, disconnect the harness connector at the CHMSL.
  2. Ignition OFF, test for less than 5.0 ohm of resistance between the ground circuit terminal B and ground.
    • If the test lamp illuminates, test the supply voltage circuits for a short to voltage.
  3. Connect a test lamp between the supply voltage circuit terminal A and the ground circuit terminal B.
  4. Ignition ON, apply and release the brake pedal. The test lamp should turn ON and OFF as the brake pedal is applied and released.
    • 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.
  5. If all circuits test normal, replace the CHMSL.
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