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Home >> Buick >> 2018 >> Regal GS >> Repair and Diagnosis >> Accessories & Equipment >> Interior/Illumination Lights >> Lighting System - Diagnostic Information And Procedures (B388B-P0504) And Symptoms >> Diagnostic Information and Procedures >> Backup Lamps Malfunction >> Circuit/System Testing

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the B16 Backup Lamp Switch.
  2. Test for less than 5 Ω between the ground circuit harness connector terminal 2 and ground.
    • If greater than the specified value, test the ground circuit for an open/high resistance.
  3. Disconnect the X1 harness connector at the K20 Engine Control Module.
  4. Ignition ON, test for less than 0.3 V at the B16 Backup Lamp Switch signal circuit harness connector terminal 1 and ground.
    • If greater than the specified value, test the signal circuit for a short to voltage.
  5. Ignition OFF, test for infinite resistance between the B16 Backup Lamp Switch signal circuit harness connector terminal 1 and ground.
    • If lower than the specified value, test the signal circuit for a short to ground.
  6. Connect the harness connector at the B16 Backup Lamp Switch.
  7. Reversing gear engaged, test for less than 5 Ω between the K20 Engine Control Module X1 harness connector terminal 71 and ground.
    • If greater than the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, test or replace the B16 Backup Lamp Switch.
  8. Reversing gear disengaged, test for infinite resistance between the K20 Engine Control Module X1 harness connector terminal 71 and ground.
    • If lower than the specified value, test or replace the B16 Backup Lamp Switch.
  9. If all the circuits test normal, replace the K20 Engine Control Module.
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