TCC COAST RELEASE RELAY NOISE WHEN DECELERATING

SOME 1982 CENTURYS WITH 3.0L ENGINES HAVE AN AUDIBLE TONE (HUM OR BUZZ) WHEN DECELERATING BETWEEN 35 AND 15 MPH DURING APPLICATION OF THE BRAKES. THE CONDITION RESULTS FROM AN ELECTRICAL FEEDBACK TO THE TCC COAST RELEASE RELAY WHICH CAUSES IT TO RESONATE AT APPROXIMATELY 500 HZ. TO CORRECT THIS CONDITION IN PRODUCTION, A DIODE WAS ADDED IN THE CIRCUIT (PURPLE WIRE WITH WHITE STRIPE) BETWEEN THE TCC SOLENOID AND TCC COAST RELEASE RELAY. THIS DIODE WAS USED FOR A SHORT PERIOD OF TIME UNTIL A WIRING CIRCUIT CHANGE WAS INCORPORATED INTO THE MAIN ENGINE HARNESS ASSEMBLY WHICH CORRECTS THE CONDITION WITHOUT REQUIRING A DIODE. TO CORRECT THIS NOISE CONDITION ON AN EARLY VEHICLE, PROCEED AS FOLLOWS: 1.REMOVE THE ELECTRICAL TAPE FROM THE WIRES AT THE THREE (3) FRONT OF DASH RELAY CONNECTORS TO EXPOSE THE 'LOOPED' PURPLE WIRE IN THE TCC COAST CONNECTOR. REFER TO ILLUSTRATION. THE TCC CONNECTOR IN MOST CASES WILL GO TO THE RELAY SHOWN IN VIEW 'A' OF THE ILLUSTRATION. IT IS POSSIBLE THAT THIS CONNECTOR MAY BE CONNECTED TO ONE OF THE OTHER RELAYS WITHOUT AFFECTING THE OPERATION OF THE VEHICLE AS THESE RELAYS ARE INTERCHANGEABLE. 2.TWO (2) PURPLE WIRES ENTER ONE (1) CAVITY OF THE TCC CONNECTOR. CUT END OF 'LOOPED' PURPLE WIRE AT THIS CONNECTOR CAVITY AS SHOWN. 3.SPLICE LOOSE END OF LOOPED PURPLE WIRE (DOTTED LINE ON ILLUSTRATION) TO A PINK-BLACK STRIPE WIRE IN ADJACENT RELAY CONNECTOR. 4.APPLY BLACK ELECTRICAL TAPE TO LOOSE END OF WIRE AT TCC CONNECTOR AND OVER SPLICED CONNECTION AT PINK-BLACK STRIPE WIRE. 5.REINSTALL THE ELECTRICAL TAPE REMOVED IN STEP 1.

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.