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Home >> Buick >> 2018 >> Enclave Base >> Repair and Diagnosis >> External Pages >> Different car >> Section 27 (Battery, Charging System And Starting System) >> Diagnostic Information and Procedures >> DTC P0621: Generator L-Terminal Circuit >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2017 GMC Acadia Limited, 2017 Chevrolet Traverse, and 2017 Buick Enclave. However, it is still accessible from the selected car via links, so may be relevant.
  1. Verify a test lamp illuminates between the G13 Generator B+ circuit terminal A X1, A X2, B X2, 1 X1 or 1 X2 and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Remove the test lamp and disconnect the B+ cable at the G13 Generator
    2. Test for less than 2 Ω in the B+ circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.
    • If the test lamp does not illuminate and the circuit fuse is open 
    1. Remove the test lamp, disconnect the battery negative cable, and disconnect the G13 Generator B+ cable.
    2. Test for infinite resistance between the B+ circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace G13 Generator.
    • If the test lamp illuminates 
  2. Disconnect the X1 harness connector at the G13 Generator, engine running.
  3. Test for 1 V or greater between the control circuit terminal 1 X1 and ground.
    • If less than 1 V 
    1. Ignition OFF, disconnect the harness connectors at the K20 Engine Control Module.
    2. Test for infinite resistance between the control circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in the control circuit end to end.
      • If greater than 2 Ω, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K20 Engine Control Module.
    • If 1V or greater 
  4. Ignition OFF, disconnect the harness connectors at the K20 Engine Control Module, Ignition ON
  5. Test for less than 1 V between the G13 Generator control circuit terminal 1 X1 and ground.
    • If greater than 1 V 

      Repair the short to voltage on the circuit.

    • If 1V or less 
  6. Test or replace the G13 Generator.
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