CAMPAIGN: ECM CIRCUIT DEACTIVATES RWAL

GROUP: 6D - ENGINE ELECTRICAL

SUBJECT: ECM CIRCUIT DEACTIVATES RWAL

MODELS: 1988 CK 200 WITH 6.2L DIESEL ENGINE (LH6) AND THM 700-R4 AUTOMATIC TRANSMISSION (MD8)

GENERAL MOTORS HAS DETERMINED THAT ON SOME 1988 CK 200 PICKUP TRUCKS BUILT BEFORE EARLY OCTOBER, 1987 AND EQUIPPED WITH 6.2L DIESEL ENGINES (LH6) AND THM 700-R4 AUTOMATIC TRANMISSIONS (MD8) THE REAR WHEEL ANTI-LOCK BRAKE (RWAL) FEATURE WILL BE DISABLED WHEN THE TORQUE CONVERTER CLUTCH (TCC) IS NOT ENGAGED. A LATENT CIRCUIT PATH IN THE ECM CAUSES A VOLTAGE FEEDBACK THROUGH THE TCC SOLENOID TO THE RWAL BRAKE SIGNAL INPUT CIRCUIT PREVENTING THE RWAL FROM DETECTING THE APPLICATION OF THE BRAKE.

THE LOSS OF THE RWAL FEATURE DOES NOT CAUSE A LOSS OF REAR BRAKES. THE BRAKE SYSTEM ON THESE VEHICLES IS NOMINALLY FRONT BIASED THROUGHOUT THE VEHICLES LOAD RANGE. THIS BRAKE SYSTEM MEETS MVSS 105 REQUIREMENTS AND IS BALANCED TO GIVE PROPER BRAKE CONTROL WHETHER OR NOT THE REAR WHEEL ANTI-LOCK BRAKE SYSTEM IS FUNCTIONING.

TO PREVENT THE POSSIBILITY OF THIS CONDITION OCCURRING IT WILL BE NECESSARY TO INSTALL A JUMPER WIRE HARNESS BETWEEN THE TRANSMISSION CONNECTION AND THE ENGINE WIRE HARNESS ON ALL INVOLVED VEHICLES.

VEHICLES INVOLVED

INVOLVED ARE CERTAIN 1988 CK 200 PICKUP TRUCKS BUILT BEFORE EARLY OCTOBER, 1987 AND EQUIPPED WITH 6.2L DIESEL ENGINES (LH6) AND THM 700-R4 AUTOMATIC TRANSMISSIONS (MD8) BUILT WITHIN THE THE FOLLOWING VIN BREAKPOINTS:

DIVISION BULL. NUM. YEAR PLANT FROM THROUGH

CHEVROLET 88C13 1988 -- JE100027 JE144158

" " " -- JZ117957 JZ162402

" " " -- J1143084 J1171232

TRUCK AND BUS 88C08 1988 PONTIAC JE500012 JE514758

" " " FORT WAYNE JZ501418 JZ518317

" " " OSHAWA J1522327 J1526975

THE SPECIFIC VEHICLES INVOLVED IN THIS CAMPAIGN HAVE BEEN IDENTIFIED BY VEHICLE IDENTIFICATION NUMBER COMPUTER LISTINGS. THESE LISTINGS ARE FURNISHED TO ALL INVOLVED DEALERS WITH THE CAMPAIGN BULLETIN.

DEALER CAMPAIGN RESPONSIBILITY

DEALERS ARE TO SERVICE ALL VEHICLES SUBJECT TO THIS CAMPAIGN AT NO CHARGE TO OWNERS, REGARDLESS OF MILEAGE, AGE OF VEHICLE, OR OWNERSHIP, FROM THIS TIME FORWARD.

WHENEVER A VEHICLE SUBJECT TO THIS CAMPAIGN IS TAKEN INTO YOUR NEW OR USED VEHICLE INVENTORY, OR IT IS IN YOUR DEALERSHIP FOR SERVICE IN THE FUTURE, YOU SHOULD TAKE THE STEPS NECESSARY TO ENSURE THE CAMPAIGN CORRECTION HAS BEEN MADE BEFORE RESELLING OR RELEASING THE VEHICLE.

OWNERS OF VEHICLES RECENTLY SOLD FROM YOUR NEW VEHICLE INVENTORY ARE TO BE CONTACTED BY THE DEALER AND ARRANGEMENTS MADE TO MAKE THE REQUIRED CORRECTION ACCORDING TO INSTRUCTIONS CONTAINED IN THIS BULLETIN.

IF NO OWNER'S NAME AND ADDRESS WERE AVAILABLE TO GMC TRUCK DIVISION AT THE TIME OF CAMPAIGN INITIATION, THE DEALER WILL DETERMINE THE OWNER'S NAME AND ADDRESS FROM THE DEALERSHIP SALES RECORDS. PLEASE PROVIDE THIS INFORMATION DIRECTLY ON THE SECOND COPY OF THE LISTING NEXT TO THE APPLICABLE VIN SO THAT OUR RECORDS MAY BE UPDATED AND THE APPROPRIATE NOTIFICATION MAILED TO THE OWNER. THIS SECOND COPY SHOULD THEN BE SUBMITTED TO THE ADDRESS LISTED BELOW IN THE PREVIOUSLY SUPPLIED YELLOW CAMPAIGN ENVELOPES.

GMC TRUCK DIVISION GENERAL MOTORS CORPORATION 101 UNION STREET PLYMOUTH, MICHIGAN 48170

OWNER NOTIFICATION

OWNERS WILL BE NOTIFIED OF THIS CAMPAIGN ON THEIR VEHICLES BY GMC TRUCK DIVISION (SEE COPY OF OWNER LETTER INCLUDED WITH THIS BULLETIN). A LISTING OF OWNER NAMES AND ADDRESSES HAS BEEN FURNISHED TO THE INVOLVED DEALERS TO ENABLE DEALERS TO FOLLOW UP WITH OWNERS INVOLVED IN THIS CAMPAIGN. THIS LISTING MAY CONTAIN OWNER NAMES AND ADDRESSES OBTAINED FROM STATE MOTOR VEHICLE REGISTRATION RECORDS. THE USE OF SUCH MOTOR VEHICLE REGISTRATION DATA FOR ANY OTHER PURPOSE IS A VIOLATION OF LAW IN SEVERAL STATES. ACCORDINGLY, YOU ARE URGED TO LIMIT THE USE OF THIS LISTING TO THIS CAMPAIGN.

SERVICE PROCEDURE

1. DISCONNECT ENGINE HARNESS TCC CONNECTOR FROM TRANSMISSION (SEE FIGURE 1).

2. PLUG JUMPER HARNESS INTO TRANSMISSION AND ENGINE TCC CONNECTORS.

3. TIE-WRAP ENGINE AND TRANSMISSION TCC CONNECTORS BACK TO BODY OF HARNESS.

PARTS INFORMATION

JUMPER WIRE HARNESSES HAVE BEEN SHIPPED DIRECTLY TO THE INVOLVED DEALERS. THESE PARTS ARE NOT TO BE ORDERED FROM GENERAL MOTORS SERVICE PARTS OPERATION (GMSPO). IF ADDITIONAL PARTS ARE REQUIRED, PLEASE CALL: ADISTRA CORPORATION, (313) 425-2600, EXTENSION 369.

PART NUMBER DESCRIPTION QUANTITY

12072777 JUMPER WIRE HARNESS 1

3816659 TIE-WRAP 1

WARRANTY INFORMATION

DEALERS SHOULD SUBMIT A WARRANTY CLAIM ON EACH VEHICLE COMPLETED UNDER THIS CAMPAIGN.

LABOR OPERATION **PARTS *TIME TROUBLE NUMBER DESCRIPTION ALLOWANCE ALLOWANCE CODE

V4710 INSTALL JUMPER $ 1.80 .2 HR 96 WIRE HARNESS

*FOR DEALER TO RECEIVE ADMINISTRATIVE TIME ALLOWANCE ASSOCIATED WITH THIS CAMPAIGN, ADD 0.1 HOUR TO THE LABOR OPERATION TIME ALLOWANCE.

**THE $1.80 AMOUNT IDENTIFIED IN THE "PARTS ALLOWANCE" COLUMN ABOVE REPRESENTS 30% OF DEALER NET FOR PARTS THAT WERE FURNISHED BY GMC TRUCK DIVISION. THIS AMOUNT IS TO BE PLACED IN THE NET ITEM AMOUNT COLUMN OF THE CLAIM AND USE TYPE CODE "M".

CAMPAIGN IDENTIFICATION LABEL

EACH VEHICLE CORRECTED IN ACCORDANCE WITH THE INSTRUCTIONS OUTLINED IN THIS PRODUCT CAMPAIGN BULLETIN WILL REQUIRE A "CAMPAIGN IDENTIFICATION LABEL". EACH LABEL PROVIDES A SPACE TO INCLUDE THE FIVE (5) DIGIT DEALER CODE OF THE DEALER PERFORMING THE CAMPAIGN SERVICE. THIS INFORMATION MAY BE INSERTED WITH A TYPEWRITER OR BALL POINT PEN.

EACH "CAMPAIGN IDENTIFICATION LABEL" IS TO BE LOCATED ON THE RADIATOR CORE SUPPORT IN AN AREA WHICH WILL BE VISIBLE WHEN THE VEHICLE IS BROUGHT IN FOR PERIODIC SERVICING BY THE OWNER.

APPLY "CAMPAIGN IDENTIFICATION LABEL" ONLY ON A CLEAN DRY SURFACE.

ADMINISTRATIVE PROCEDURE

PROCEDURES COVERING THIS CAMPAIGN ARE OUTLINED IN SECTION V OF YOUR DEALERSHIP'S "GMC TRUCK CLAIMS PROCESSING MANUAL" #P 8719.

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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.