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Home >> Chevrolet >> 2006 >> Optra5 LT, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - 1.6L (L91) >> Diagnostic Information and Procedures >> DTC P0400, P0401, P0402, or P1402 >> Circuit/System Testing

Circuit/System Testing

  1. Verify that one of the following conditions is not present:
    • Incorrect EGR valve for engine application.
    • A vacuum leak between the EGR valve and the intake manifold.
    • Signs of external leakage usually indicated by carbon buildup around the mating surfaces of the components or an audible exhaust noise.
    • Restrictions in the passages or EGR valve caused by carbon deposits or casting flash.
    • Restrictions in EGR pipe caused by carbon deposits or casting flash.
    • Leaks or restrictions at the manifold absolute pressure (MAP) sensor.
      • IMPORTANT: Restrictions can cause excessive back pressure and low engine vacuum.
    • Leaking, restricted, or modified exhaust system-Refer to Symptoms - Engine Exhaust .
    • Mechanical failure in the engine such as worn piston rings, camshaft or incorrect timing belt installation-Refer to Symptoms - Engine Mechanical .
  2. If all conditions test normal, replace the EGR valve.
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