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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 P2687 >> Circuit/System Testing
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Circuit/System Testing

  1. Ignition OFF, disconnect the fuel heater relay from the underhood auxiliary fuseblock.
  2. Connect a test lamp between the control circuit terminal 86 and 12 volts.
  3. Ignition ON, command the fuel heater ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM.
    • If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
  4. Ignition OFF, connect a test lamp between the control circuit terminal 86 and the ignition 1 voltage circuit terminal 85.
  5. Ignition ON, command the fuel heater ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always OFF, repair the ignition 1 voltage circuit for an open/high resistance.
  6. If all circuits test normal, test or replace the fuel heater relay.
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