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Home >> Hummer >> 2008 >> H3 Base, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 178 (Battery, Charging System And Starting System) >> Diagnostic Information and Procedures >> DTC P0621 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2008 Cadillac STS. 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 generator turn on signal circuit for a short to voltage. If the circuit tests nor mal, replace the ECM.
  3. Engine Running, test for greater than 3.5 volts between the generator turn on signal circuit terminal 1 and ground.
    • If less than the specified range, test the generator turn on signal circuit for a short to ground or an open/high resistance. If the circuit tests nor mal, replace the ECM.
  4. If the circuit tests nor mal, test or replace the generator.
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