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Home >> Cadillac >> 2012 >> Escalade EXT >> Repair and Diagnosis >> External Pages >> Different car >> Section 1775 (Battery, Charging System And Starting System) >> Diagnostic Information and Procedures >> DTC P0621 >> Circuit/System Testing
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Circuit/System Testing

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  1. Verify that a test lamp illuminates between the G13 generator B+ terminal 1 X2 and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Ignition OFF.
    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. Ignition OFF.
    2. Test for greater than 100 Ω between the B+ circuit and ground.
      • If 100 Ω or less, repair the short to ground on the circuit.
      • If greater than 100 Ω, replace the generator.
    • If the test lamp illuminates 
  2. Ignition OFF, disconnect the X1 harness connector at the generator, ignition ON.
  3. Test for 4.5-5.5 V between the control circuit terminal 1 X1 and ground.
    • If less than 4.5 V 
    1. Ignition OFF, disconnect the harness connectors at the ECM.
    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 the 2 Ω, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the ECM.
    • If greater the 5.5 V 
    1. Ignition OFF, disconnect the harness connectors at the ECM, ignition ON.
    2. Test for less than 1 V between the control circuit and ground.
      • If greater than 1 V, repair the short to voltage on the circuit.
      • If less than 1 V, replace the ECM.
    • If between 4.5-5.5 V 
  4. Test or replace the generator.
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