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Home >> Chevrolet >> 2005 >> Impala LS >> Repair and Diagnosis >> External Pages >> Different car >> Section 902 (Battery, Charging System And Starting System) >> Diagnostic Information and Procedures >> DTC P0621 >> Circuit/System Testing
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Circuit/System Testing

WARNING: This page is about a different car, the 2008 Chevrolet Malibu. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the harness connector at the generator.
  2. Ignition ON, test for less than 1 volt between the generator turn on signal circuit terminal 1 and ground.
    • If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  3. Engine running, command the GEN L-Terminal ON with a scan tool. Test for greater than 3.5 volts between the signal circuit terminal 1 and ground.
    • If less than the specified range, test the signal circuit for a short to ground, an open or a high resistance. If the circuit tests normal, replace the ECM.
  4. If the circuit tests normal, test or replace the generator.
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