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Home >> Chevrolet >> 2006 >> Cobalt LTZ >> Repair and Diagnosis >> External Pages >> Different car >> Section 793 (Engine Controls And Fuel - 2.0L - DTC P0243 To DTC P0700) >> DTC P0685, P0686, P0687, P0689, or P0690 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2008 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the Powertrain Relay.
  2. Ignition ON, verify that a test lamp does not illuminate between the ignition circuit terminal 30 and ground.
    • If the test lamp illuminates, test the ignition circuit for a short to voltage.
  3. Ignition OFF, verify that a test lamp illuminates between the B+ circuit terminal 86 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  4. Verify that a test lamp illuminates between the B+ circuit terminal 87 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
  5. Disconnect the X2 harness connector at the ECM.
  6. Test for less than 2 ohms between ground and the following terminals:
    • ECM terminal 1 X2
    • ECM terminal 2 X2
    • ECM terminal 4 X2
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Ignition ON, verify that a test lamp illuminates between connector terminal 54 X2 and ground.
    • If the test lamp does not illuminate, test the circuit for an open/high resistance and a short to ground. If the circuit tests normal and its fuse is open, replace the ECM.
  8. Ignition OFF, connect the harness connector at the ECM.
  9. Ignition ON, connect a jumper wire between the B+ circuit terminal 87 and the ignition circuit terminal 30. Verify that the scan tool communicates and that the EC Ignition Relay Feedback Signal parameter indicates B+ voltage.
    • If not the specified value or if the scan tool does not communicate, test the ignition circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  10. Ignition OFF, remove the jumper wire. Allow the ECM to completely power down.
  11. Connect a DMM, set on the diode setting, between the control circuit terminal 85 and ground.
  12. Ignition OFF, the DMM reading should be greater than 2.5 volts or display Open Loop.
    • If less than the specified value, test the control circuit for a short to voltage or short to ground. If the circuits test normal, replace the ECM.
  13. Ignition ON, the DMM reading should be less than 1 volt.
    • If greater than the specified range, test the control circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  14. If all circuits test normal, replace the Powertrain Relay.
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