INFO ON DTC P1404 DUE TO INCORRECT REINSTALLATION OF

THIS IS A MONTHLY SERVICE NEWSLETTER ARTICLE. THIS BULLETIN IS NOT INTENDED FOR PUBLICATION.

SUBJECT: INFORMATION ON DTC P1404 DUE TO INCORRECT REINSTALLATION OF EGR VALVE AFTER REPAIR

MODELS: 1998 BUICK SKYLARK 1998 BUICK CENTURY WITH L82 3.1L VIN M ENGINE

ROUGH IDLE OR SURGE AT IDLE. MIL ILLUMINATED WITH DTC P1404 (EGR VALVE STUCK OPEN). CONDITION WILL OCCUR HOT/COLD.

THE EGR VALVE MAY BE INSTALLED BACKWARDS (INCORRECTLY) AFTER A REPAIR HAS BEEN PERFORMED INVOLVING EGR VALVE REMOVAL, E.G., FUEL INJECTOR REPLACEMENT.

THE EGR VALVE CAN BE INSTALLED IN EITHER DIRECTION. THE INTAKE PLENUM HAS TWO OPENINGS TO ACCOMMODATE THE EGR VALVE. IF INSTALLED PROPERLY, THE EGR PINTLE WILL BE ON THE INTAKE PLENUM VACUUM PORT SIDE. IF INSTALLED INCORRECTLY, THE PINTLE WILL BE ON THE EXHAUST SIDE OF THE PLENUM PORT. THE NORMAL COMMANDED STATE OF THE EGR VALVE AT IDLE IS 0%. IF THE EGR VALVE IS INSTALLED INCORRECTLY, SCAN TOOL DATA PARAMETER WILL INDICATE: EGR COMMANDED 0% AND ACTUAL POSITION WILL BE BETWEEN 5-20%. THIS SITUATION WILL THEN ALLOW ENGINE VACUUM AT IDLE TO ACT ON THE EGR VALVE PINTLE; RESULTING IN A 5-20% PINTLE OPENING. EXHAUST GASES THEN FLOW INTO THE INTAKE PLENUM; RESULTING IN ROUGH/SURGE IDLE CONDITION AND DTC P1404 (DTC IS A TYPE B CODE REQUIRING TWO CONSECUTIVE TRIPS TO SET).

FIGURES: 00 ATTACHMENTS: 00

GENERAL MOTORS BULLETINS ARE INTENDED FOR USE BY PROFESSIONAL TECHNICIANS, NOT A "DO-IT-YOURSELFER". THEY ARE WRITTEN TO INFORM THOSE TECHNICIANS OF CONDITIONS THAT MAY OCCUR ON SOME VEHICLES, OR TO PROVIDE INFORMATION THAT COULD ASSIST IN THE PROPER SERVICE OF A VEHICLE. PROPERLY TRAINED TECHNICIANS HAVE THE EQUIPMENT, TOOLS, SAFETY INSTRUCTIONS AND KNOW-HOW TO DO A JOB PROPERLY AND SAFELY. IF A CONDITION IS DESCRIBED, DO NOT ASSUME THAT THE BULLETIN APPLIES TO YOUR VEHICLE, OR THAT YOUR VEHICLE WILL HAVE THAT CONDITION. SEE A GENERAL MOTORS DEALER SERVICING YOUR BRAND OF GENERAL MOTORS VEHICLE FOR INFORMATION ON WHETHER YOUR VEHICLE MAY BENEFIT FROM THE INFORMATION.

COPYRIGHT 1998 GENERAL MOTORS CORPORATION. ALL RIGHTS RESERVED.