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Home >> Chevrolet >> 2008 >> Optra LS, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls And Fuel - 2.0L (Diesel) >> Diagnostic Information and Procedures >> DTC P0683 >> Circuit/System Testing
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Circuit/System Testing

  1. Ignition OFF, and the MAIN fuse removed, disconnect the harness connector at the glow plug control module.
  2. Test for less than 5 ohms of resistance between the glow plug control module ground circuit terminal 7 and ground.
    • If greater than the specified range, repair the ground circuit for an open/high resistance.
  3. Install the MAIN fuse. Ignition ON, verify a test lamp illuminates between the ignition 1 voltage circuit terminal 6 and ground.
    • If the test lamp does not illuminate, repair the ignition 1 voltage circuit for a short to ground or an open/high resistance.
  4. Test for greater than 10 volts between the glow plug control module control circuit terminal 10 and ground.
    • If less than the specified range, test the control circuit for an open or a short to ground. If the circuit tests normal, replace the ECM.
  5. Test for greater than 10 volts between the glow plug control module communication circuit terminal 9 and ground.
    • If less than the specified range, test the communication circuit for an open or a short to ground. If the circuit tests normal, replace the ECM.
  6. Test the DC frequency from the glow plug control module control circuit terminal 10. Command the glow plug control module ON with a scan tool. Verify the DC frequency is between 30-35 Hz.
    • If less than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the ECM.
    • If greater than the specified range, test the control circuit for a high resistance. If the circuit tests normal, replace the ECM.
  7. Test the AC frequency from the glow plug control module communication circuit terminal 9. Command the glow plug control module ON with a scan tool. Verify the AC frequency is between 30-35 Hz.
    • If less than the specified range, test the communication circuit for a short to voltage. If the circuit tests normal, replace the ECM.
    • If greater than the specified range, test the communication circuit for a high resistance. If the circuit tests normal, replace the ECM.
  8. If all circuits test normal, test or replace the glow plug control module.
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