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Home >> Chevrolet >> 2008 >> Optra LS, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls And Fuel - 1.4L DOHC >> Diagnostic Information and Procedures >> DTC P1511, P1512, or P1513 >> Circuit/System Testing

Circuit/System Testing

  1. Verify the following conditions do not exist:
    • The throttle body is not damage or modified
    • Vacuum leaks
    • A restricted air intake system
    • Excessive deposits on the throttle plate or bore
    • The throttle shaft for binding
    • The throttle linkage or the throttle cable for binding
    • Incorrectly installed PCV valve or hose
    • A malfunctioning PCV valve
    • If you find any of the above conditions, repair as necessary.
  2. Ignition OFF, disconnect the harness connector at the ISC motor.
  3. Ignition ON, test for less than 0.3 volt between the high control circuit terminal 4 and 12 volts.
    • If greater than the specified range, test the high control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
    4. IMPORTANT: Use the AC volt scale on the DMM. The millivolt scale will produce an inaccurate reading.
  4. Engine running, test for 30-40 hertz on the AC scale between the high control circuit terminal 4 and ground.
    • If not within the specified range, test the high control circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  5. Ignition OFF, connect a test lamp between the low control circuit terminal 6 and 12 volts.
    • If test lamp illuminates, test the low control circuit for a short to ground. If the circuit tests normal, replace the ECM.
  6. Ignition ON, test for less than 0.3 volt between the low control circuit terminal 6 and ground.
    • If greater than the specified range, test the low control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
  7. Test for 4.8-5.2 volts between the 5-volt reference circuit terminal 2 and ground.
    • If less than the specified range, test the 5-volt reference circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the ECM.
  8. If all circuits test normal, test or replace the ISC motor.
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