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Home >> Cadillac >> 2007 >> Escalade EXT >> Repair and Diagnosis >> External Pages >> Different car >> Section 1871 (Immobilizer System) >> Diagnostic Information and Procedures >> DTC P254F >> Circuit/System Testing
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Circuit/System Testing

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  1. Ignition OFF, disconnect the harness connector at the hood ajar switch.
  2. Ignition OFF, test for less than 10 ohms between the ground circuit terminal C and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, test for 10.0-12.5 volts between the signal circuit terminal A 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.
    • 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. Ignition ON, test for 10.0-12.5 volts between the signal circuit terminal B 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.
    • 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.
  5. If all circuits test normal, test or replace the hood ajar switch.
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