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Home >> Buick >> 2007 >> Allure CX >> Repair and Diagnosis >> External Pages >> Different car >> Section 62 (Wiring Systems And Power Management - DTC B1370 To DTC B1475) >> DTC B1428 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2008 Buick LaCrosse and 2008 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.

L26, L32

  1. Ignition OFF, disconnect the IGN 1 Relay 37.
  2. Test for less than 1 ohm of resistance between the ground circuit terminal C7 and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the ignition 1 voltage circuit terminal A8 and ground.
  4. Command the Ignition Power Relay 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 ignition 1 voltage 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.
  5. If all circuits test normal, test or replace the IGN 1 relay.

LS4

  1. Ignition OFF, disconnect the harness connector X1 of the underhood fuse block.
  2. Test for less than 1 ohm of resistance between the IGNITION MAIN PCB Relay ground circuit terminal C2 and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Disconnect the harness connector X4 of the underhood fuse block.
  4. Connect a test lamp between the ignition 1 voltage circuit terminal H1 and ground.
  5. Command the Ignition Power Relay 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 ignition 1 voltage 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.
  6. If all circuits test normal, test or replace the underhood fuse block.
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