SMU - SECTION 5E1C - VCM (L35) FOURWHEEL. Chevrolet Blazer

SUBJECT: SERVICE MANUAL UPDATE - SECTION 5E1C - VCM (L35) FOURWHEEL ANTILOCK BRAKES - REVISED DTC CHART 65

MODELS: 1995 CHEVROLET AND GMC S/T MODELS

DURING THE KELSEY-HAYES ABS EBC4 MANUFACTURING PROCESS, SILICONE ASSEMBLY FLUID WAS USED TO INSTALL SEALS, VALVES, AND DIAPHRAGMS. IN SOME CASES, THIS FLUID MAY MIGRATE ONTO THE UNSEALED ABS RELAY CONTACTS.

THE PROBLEM OCCURS WHEN A SPARK IS CREATED BETWEEN THE CONTACTS AS THE VCM COMMANDS THE ABS RELAY TO CLOSE. THE COMBINATION OF SILICONE ASSEMBLY FLUID AND HEAT CREATED BY THE ARCING CONTACTS CAN CAUSE THE SILICONE TO SOLIDIFY. THE SOLIDIFIED SILICONE BECOMES AN INSULATOR BETWEEN THE RELAY CONTACTS CAUSING LOW VOLTAGE FAULTS.

ENGINEERING HAS DETERMINED THAT THIS PROBLEM CAN BE DETECTED BY THE PRESENCE OF A DTC 65 WITH A DTC 68 SET ALSO. THE ATTACHED DIAGNOSTIC CHART IS AN UPDATE AND SHOULD BE USED IN PLACE OF THE CURRENT CHART FOR THE 1995 S/T SECTION 5E1C, PAGE 5E1C-65.

THIS PROBLEM MAY EXIST IN 1995 S/T ABS UNITS (PART #15971559) WHEN USED IN CONJUNCTION WITH THE VCMX-A.

AT THE END OF THE 95 MODEL YEAR (JUNE), THE ABS RELAY WAS CHANGED TO A SEALED RELAY. THE SEALED RELAY WILL PROHIBIT ASSEMBLY FLUID FROM MIGRATING ONTO THE RELAY CONTACTS, RESOLVING THE ISSUE. ALL SERVICE PARTS MANUFACTURED SINCE JULY 1995 WILL HAVE THE SEALED RELAY.

FIGURES: 0 ATTACHMENTS: 3

Object Number: 76715 Size: FS

Object Number: 76174 Size: FS

Object Number: 76173 Size: FS

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.