EXCESSIVE AM RADIO STATIC NOISE WITH ENGINE RUNNING

SUBJECT: EXCESSIVE AM RADIO STATIC NOISE WITH ENGINE RUNNING (GROUND EXHAUST SYSTEM TO VEHICLE UNDERBODY)

MODELS: 1994-95 BUICK LESABRE, PARK AVENUE 1995 BUICK RIVIERA 1994-95 CADILLAC CONCOURS, DEVILLE, ELDORADO, SEVILLE 1994-95 OLDSMOBILE EIGHTY EIGHT, NINETY EIGHT 1995 OLDSMOBILE AURORA 1994-95 PONTIAC BONNEVILLE

CONDITION:

SOME OWNERS MAY COMMENT ON EXCESSIVE STATIC NOISE NOTED WHILE LISTENING TO AM RADIO STATIONS WITH THE ENGINE RUNNING. NOISE DISSIPATES WHEN THE ENGINE IS TURNED OFF.

CAUSE:

IGNITION NOISE IS TRANSMITTED FROM THE ENGINE TO THE EXHAUST SYSTEM. BECAUSE NVH CONCERNS HAVE RESULTED IN THE EXHAUST SYSTEM BEING SUSPENDED BY RUBBER LINED HANGERS, THE SYSTEM IS NOT GROUNDED. THE EXHAUST SYSTEM ACTS AS AN ANTENNA AND REBROADCASTS THE IGNITION NOISE, HAVING THE GREATEST IMPACT ON AM BAND RECEPTION.

CORRECTION:

GROUND THE EXHAUST SYSTEM TO THE VEHICLE UNDERBODY USING THE FOLLOWING PROCEDURE:

MATERIALS NEEDED:

1. ONE 1/4 - 3/8 INCH WIDE BRAIDED GROUND STRAP WITH A CRIMP-ON RING TERMINAL ON AT LEAST ONE END.

2. ONE #10 OR LARGER SHEET METAL SCREW.

3. ONE STAINLESS STEEL HOSE CLAMP WITH A DIAMETER TO MATCH THE EXHAUST SYSTEM BEING MODIFIED.

IMPORTANT: CLEAN ATTACHMENT AREA BEFORE SECURING HOSE CLAMP TO ENSURE A GOOD GROUND CONNECTION.

INSTALL OR CONNECT:

1. HOSE CLAMP (FIGURE 1, ITEM 1) AROUND EXHAUST SYSTEM JUST REARWARD OF THE CATALYTIC CONVERTER.

2. BARE END OF GROUND STRAP (FIGURE 1, ITEM 4) BETWEEN HOSE CLAMP AND EXHAUST. FULLY TIGHTEN CLAMP.

3. GROUND STRAP RING TERMINAL (FIGURE 1, ITEM 3) TO UNDERBODY USING SHEET METAL SCREW. LOCATE AN UNUSED FLOORPAN HOLD OR DRILL PILOT HOLE IN NEARBY HEAT SHIELD TO MATCH SCREW SIZE (FIGURE 1, ITEM 2). KEEP HOLE AS CLOSE TO THE HOSE CLAMP AS POSSIBLE. MAKE SURE GROUND STRAP IS NOT STRETCHED TIGHT AND ALLOWS FOR NORMAL EXHAUST SYSTEM MOVEMENT.

WARRANTY INFORMATION:

FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OPERATION NUMBER: N6478 LABOR TIME: 0.3 HRS.

FIGURES: 1 ATTACHMENTS: 0

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 1995 GENERAL MOTORS CORPORATION. ALL RIGHTS RESERVED.