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Home >> Pontiac >> 2009 >> G8 Base >> Repair and Diagnosis >> External Pages >> Different car >> Section 12 (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 Pontiac G8. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the X1 harness connector at the generator.
  2. Ignition ON, test for less than 1 V between the 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, test for greater than 3.5 V between the signal circuit terminal 1 and ground.
    • If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
  4. If the circuit tests normal, replace the generator.
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