LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Chevrolet >> 2008 >> HHR SS, Standard >> Repair and Diagnosis >> Electrical >> Charging Systems >> Battery, Charging System And Starting System >> Diagnostic Information and Procedures >> DTC P0621 >> Circuit/System Testing
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Circuit/System Testing

  1. Verify that a test lamp illuminates between the generator B+ terminal X2 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  2. Ignition OFF, disconnect the X1 harness connector at the generator.
  3. Ignition ON, test for less than 1 V between the control circuit terminal 1 and ground.
    • If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  4. Engine running, command the L-Terminal ON to 85% with a scan tool. Test for greater than 3 volts between the control circuit terminal 1 and ground.
    • If less than the specified range, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
  5. If the circuit tests normal, replace the generator.
scientia non olet · About LEMON Manuals