CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO P2237, P2238, P2239, P2252 OR P2253)
PERFORM ACTIVE TEST USING INTELLIGENT TESTER (OPERATE EGR VALVE)
CHECK WHETHER DTC OUTPUT RECURS (DTC P0401)
CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - ECM)
PERFORM CONFIRMATION DRIVING PATTERN
CHECK WHETHER DTC OUTPUT RECURS (DTC P2237, P2238, P2239, P2252 OR P2253)