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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 P0401 or P0402 >> Circuit/System Testing

Circuit/System Testing

  1. Ignition OFF, inspect for the following:
    • Intake system/charge air hoses for leaks/restrictions
    • Exhaust system/turbo charger for leaks/restrictions
    • Vacuum supply system for leaks or blockage
    • Air filter for restrictions
  2. Disconnect the vacuum source from the EGR solenoid.
  3. Connect the J 23738-A  to the EGR solenoid vacuum supply hose. Engine running, verify the vacuum is greater than 20 in Hg.
    • If less than the specified range, inspect the vacuum supply hose and filter for a leak or restriction. If the supply hose is normal, replace the vacuum pump.
  4. Connect the vacuum source to the EGR solenoid valve. Connect the J 23738-A  to the EGR vacuum port on the EGR solenoid valve. Engine running, command the EGR solenoid valve to 5 percent with a scan tool. Verify the vacuum is at 0 in Hg.
    • If greater than the specified range, replace the EGR solenoid valve.
  5. Command the EGR solenoid valve to 100 percent with a scan tool. Verify the vacuum is greater than 20 in Hg.
    • If less than the specified range, test the ignition 1 voltage circuit and the EGR solenoid control circuit for greater than 5 ohms of resistance. If the circuits test normal, replace the EGR solenoid valve.
  6. Connect the J 23738-A  to the EGR valve vacuum hose. Apply 10 in Hg of vacuum to the EGR valve. Verify the EGR valve operation.
    • If the EGR valve does not operate, inspect the vacuum hose for leaks or restrictions. If no leaks or restrictions are found, replace the EGR valve.
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