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Home >> Isuzu >> 2007 >> i-290 LS, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 39 (Lighting Systems) >> Diagnostic Information and Procedures >> Park, License, and/or Tail Lamps Malfunction >> Circuit/System Testing

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.
CAUTION: The high intensity discharge system produces high voltage and current. To reduce the risk of severe shocks and burns:
  • Never open the high intensity discharge system ballast or the arc tube assembly starter.
  • Never probe between the high intensity discharge system ballast output connector and the arc tube assembly.

Headlamp Switch Circuit Test

  1. Ignition OFF, disconnect the harness connector at the headlamp switch.
  2. Ignition OFF, verify that a test lamp illuminates between the ground circuit terminal 8 and B+.
    • If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Parklamp 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 BCM.
  4. Install a 3A fused jumper wire between the signal circuit terminal 2 and ground. Verify the scan tool Parklamp 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 BCM.
  5. If all circuits test normal, test or replace the headlamp switch.

Park, License, and/or Tail Lamps Circuit Test -- Domestic

  1. Ignition OFF, disconnect the PRK LAMP Relay from the rear fuse block.
  2. Ignition ON, verify that a test lamp does not illuminate between the supply voltage circuit terminal 104 and ground.
    • If the test lamp illuminates, test the supply voltage circuits for a short to voltage.
  3. Verify that a test lamp illuminates between the B+ circuit terminal 102 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  4. Verify that a test lamp illuminates between the B+ circuit terminal 100 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
  5. Connect a test lamp between the B+ circuit terminal 102 and the control circuit terminal 101.
  6. Command the Parking 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 ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.
    • 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 BCM.
  7. Disconnect the harness connector at the inoperative lamp.
  8. Ignition OFF, test for less than 5.0 ohms of resistance between the appropriate ground circuit terminal listed below and ground.
    • Front Park and Marker Lamp terminal A
    • Tail Lamp terminal C
    • License Lamp terminal B
    • Middle Park Lamp terminal B (V4U)
    • Rear Park Lamp terminal B (V4U or B9Q)
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  9. Connect a test lamp between the inoperative lamp supply voltage circuit terminal listed below and ground.
    • Front Park and Marker Lamp terminal B
    • Tail Lamp terminal F
    • License Lamp terminal A
    • Middle Park Lamp terminal A (V4U)
    • Rear Park Lamp terminal A (V4U or B9Q)
  10. Connect a 3A fused jumper wire between the B+ circuit terminal 100 and the supply voltage circuit terminal 104. Verify the test lamp is illuminated.
    • If the test lamp does not illuminate, test the supply voltage circuit for an open/high resistance. If the circuit tests normal, test or replace the bulb or lamp assembly.
  11. If all circuits test normal, test or replace the park lamp relay.

Park, and/or Tail Lamps Circuit Test -- Export

  1. Ignition OFF, disconnect the appropriate PRK LAMP Relay or the RT PRK LAMP Relay from the rear fuse block.
  2. Ignition ON, verify that a test lamp does not illuminate between the appropriate supply voltage circuit terminal listed below and ground.
    • PRK LAMP Relay terminal 104
    • RT PRK LAMP Relay terminal 94
    • If the test lamp illuminates, test the supply voltage circuits for a short to voltage.
  3. Verify that a test lamp illuminates between the appropriate B+ circuit terminal listed below and ground.
    • PRK LAMP Relay terminal 102
    • RT PRK LAMP Relay terminal 90
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  4. Verify that a test lamp illuminates between the appropriate B+ circuit terminal listed below and ground.
    • PRK LAMP Relay terminal 100
    • RT PRK LAMP Relay terminal 93
    • If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
  5. Connect a test lamp between the appropriate B+ circuit terminal and the control circuit terminal listed below.
    • PRK LAMP Relay terminal 101 and terminal 102
    • RT PRK LAMP Relay terminal 92 and terminal 93
  6. Command the Parking 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 ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.
    • 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 BCM.
  7. Disconnect the harness connector at the inoperative lamp.
  8. Ignition OFF, test for less than 5.0 ohms of resistance between the appropriate ground circuit terminal listed below and ground.
    • Front Park and Marker Lamp terminal A
    • Tail Lamp terminal H
    • License Lamp terminal B
    • Middle Park Lamp terminal B (V4U)
    • Rear Park Lamp terminal B (V4U or B9Q)
    • Position Lamp terminal A (T72)
    • Position Lamp terminal H ( T84)
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  9. Connect a test lamp between the inoperative lamp supply voltage circuit listed below and ground.
    • Front Park and Marker Lamp terminal B
    • Tail Lamp terminal F
    • License Lamp terminal A
    • Middle Park Lamp terminal A (V4U)
    • Rear Park Lamp terminal A (V4U or B9Q)
    • Position Lamp terminal G-- Export
  10. Connect a 3A fused jumper wire between the appropriate relay B+ circuit terminal and the supply voltage circuit terminal listed below. Verify the test lamp is illuminated.
    • PRK LAMP Relay terminal 100 and terminal 104
    • RT PRK LAMP Relay terminal 90and terminal 94
    • 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 or the lamp assembly.
  11. If all circuits test normal, test or replace the park lamp relay.

License Lamp Circuit Test -- Export

  1. Ignition OFF, disconnect the EXP LIC LAMP Relay from the rear fuse block.
  2. HVAC Control Module terminal 2 C3
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify that a test lamp does not illuminate between the supply voltage circuit terminal 10 and ground.
    • If the test lamp illuminates, test the supply voltage circuit for a short to voltage.
  4. Park lamps ON, verify that a test lamp illuminates between the supply voltage circuit terminal 6 and ground.
    • If the test lamp does not illuminate, test the supply voltage circuit for an open/high resistance.
  5. Park lamps ON, verify that a test lamp illuminates between the supply voltage circuit terminal 8 and ground.
    • If the test lamp does not illuminate, test the supply voltage circuit for an open/high resistance.
  6. Ignition OFF, disconnect the harness connector at the inoperative license lamp.
  7. Ignition OFF, test for less than 5.0 ohms of resistance between the ground circuit terminal B and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  8. Connect a test lamp between the supply voltage circuit terminal A and ground.
  9. Connect a 3A fused jumper wire between the relay supply voltage circuit terminal 10 and B+. 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 or the lamp assembly.
  10. If all circuits test normal, test or replace the EXP LIC LAMP Relay.
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