GCUS-3-421

28340 - SERVICE UPDATE. RRPROGRAM THE ENGINE CONTROL MODULE. AN ENGINE MISFIRE CONDITION COULD OCCUR DURING THE ENGINE MAINTENANCE MODE (EMM) AFTER THE VEHICLE HAS BEEN SITTING FOR AN EXTENDED PERIOD OF TIME CAUSING THE CHECK ENGINE/SERVICE ENGINE SOON LIGHT TO ILLUMINATE, A ROUGH OR HIGH IDLE CONDITION, AND DIAGNOSTIC TROUBLE CODE (DTC) P0300 TO SET. A SOFTWARE UPDATE IS AVAILABLE TO CORRECT THIS AND ALSO A CONDITION WHERE DTCS P040B, P041B, P1427 AND P1429 MAY SET INCORRECTLY.