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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1147 (Engine Controls And Fuel - 3.6L - DTC P0137 To DTC P0497) >> DTC P0449, P0498, or P0499 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the harness connector at the EVAP vent solenoid valve.
  2. Ignition ON, verify that a test lamp illuminates between the ignition voltage circuit terminal A and ground.
    • If the test lamp does not illuminate, test the ignition voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition voltage circuit fuse is open, test all components connected to the ignition voltage circuit and replace as necessary.
  3. Ignition OFF, connect a test lamp between the control circuit terminal B and the ignition voltage circuit terminal A.
    4. IMPORTANT: The control circuit for the EVAP vent solenoid valve is pulled-up to voltage within the ECM, 2.6-4.6 volts on the control circuit is normal.
  4. Ignition ON, use a scan tool to command the EVAP vent solenoid valve ON and OFF. The test lamp should turn ON and OFF.
    • If the test lamp remains ON all the time, test for a short to ground on the control circuit. If circuit/connections test normal, replace the ECM.
    • If the test lamp remains OFF all the time, test for a short to voltage or an open/high resistance on the control circuit. If circuit/connections test normal, replace the ECM.
  5. Test for 2.6-4.6 volts between the control circuit terminal B and ground.
    • If the voltage is not within the specified range, replace the ECM.
  6. If all circuits/connections test normal, test or replace the EVAP vent solenoid valve.
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