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Home >> Chevrolet >> 2004 >> Impala LS >> Repair and Diagnosis >> External Pages >> Different car >> Section 791 (Cruise Control System) >> Diagnostic Information and Procedures >> DTC P1574 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2008 Buick Lucerne. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the harness connectors at the appropriate control modules listed below.
    • ECM X1 and TCM (LD8 or L37)
    • PCM X1 and TAC (L26)
  2. Connect a test lamp between the appropriate signal circuit terminal listed below and ground.
    • TAC terminal 6 (L26)
    • TCM terminal 42
  3. Ignition ON, verify the test lamp illuminates ON and OFF while pressing and releasing the brake pedal.
    • If the test lamp is always ON, test the signal circuit for a short to voltage. If the circuit tests normal, replace the BCM.
    • If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  4. Ignition OFF, connect the harness connector at the TCM.
  5. Connect a test lamp between the appropriate signal circuit terminal listed below and ground.
    • PCM terminal 32 (L26)
    • ECM terminal 7 (LD8 or L37)
  6. Ignition ON, verify the test lamp illuminates ON and OFF while pressing and releasing the brake pedal.
    • If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the TCM.
  7. If all circuits tests normal, replace the ECM with (LD8 or L37), or PCM with (L26).
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