SMU - SECTION 3 - CONTROL MODULE SYSTEMS - REVISED. GMC Truck GMC MD Bus Chassis (B Model) 1997

SUBJECT: SERVICE MANUAL UPDATE-SECTION 3-CONTROL MODULE SYSTEMS- REVISED SEVERAL DIAGNOSTIC PROCEDURES

MODELS: 1997 CHEVROLET AND GMC T-SERIES AND C-SERIES OF THE MEDIUM DUTY TRUCKS AND B7 CHASSIS WITH 6.0L, 7.0L ENGINE (VINS P, M - RPOS LS0, LR0)

THIS BULLETIN IS BEING ISSUED TO REVISE THE FOLLOWING SERVICE MANUALS. PLEASE USE THE BULLETED LIST BELOW IN ORDER TO REFERENCE THE NEEDED CORRECTIONS FOR THE SPECIFIC SERVICE MANUAL. THE EFFECTED SERVICE MANUALS IN BOOK 2 OF 2 INCLUDES THE FOLLOWING INFORMATION:

* 1997 T-SERIES MEDIUM DUTY TRUCK * 1997 C-SERIES MEDIUM DUTY TRUCK * 1997 B7 CHASSIS

THIS BULLETIN REVISES THE FOLLOWING DIAGNOSTIC PROCEDURES: * THE ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK * THE TABLE A-1-NO MALFUNCTION INDICATOR LAMP (MIL). * THE TABLE A-2-NO SCAN DATA OR WILL NOT FLASH DTC 12. THE MALFUNCTION INDICATOR LAMP (MIL) "ON" STEADY. * THE TABLE A-3-ENGINE CRANKS BUT WILL NOT RUN. * DTC 34 MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR CIRCUIT LOW (HIGH VACUUM INDICATED).

PLEASE MAKE THE FOLLOWING CHANGES TO THE SUBJECT SERVICE MANUALS: * 1997 T-SERIES AND C-SERIES OF THE MEDIUM DUTY TRUCKS AND B7 CHASSIS. THE OBD SYSTEM CHECK. - STEP #5 YES COLUMN IS INCORRECT. THE YES COLUMN SHOULD READ GO TO STEP #6. - STEP #6 YES COLUMN IS INCORRECT. THE YES COLUMN SHOULD READ GO TO STEP #7. - STEP #7 NO COLUMN IS INCORRECT. THE NO COLUMN SHOULD READ GO TO STEP #8. - STEP #8 YES AND NO COLUMNS ARE INCORRECT. THE YES COLUMN SHOULD READ GO TO STEP #9. THE NO COLUMN SHOULD READ GO TO THE DIAGNOSTIC TABLES FOR THAT COMPONENT.

* 1997 T-SERIES OF THE MEDIUM DUTY TRUCK. THE BATTERY AND IGNITION FEED FUSES ARE INCORRECTLY LABELED IN THE ELECTRICAL SCHEMATIC FOR TABLES A-1 AND A-2. - THE AMPERAGE RATING FOR THE BATTERY FUSE #7 SHOULD READ 20 AMPS. - THE AMPERAGE RATING FOR THE IGNITION FUSE #6 SHOULD READ 15 AMPS.

* 1997 T-SERIES AND THE C-SERIES OF THE MEDIUM DUTY TRUCKS AND THE B-7 CHASSIS. - THE YES COLUMN AND THE NO COLUMN ARE INCORRECTLY NUMBERED IN TABLE A-2 UNDER STEP #9. THE YES COLUMN SHOULD READ GO TO STEP #10. THE NO COLUMN SHOULD READ GO TO STEP #13.

* 1997 T-SERIES AND THE C-SERIES OF THE MEDIUM DUTY TRUCKS AND THE B-7 CHASSIS. - THE YES COLUMN IS INCORRECTLY NUMBERED IN TABLE A-3 UNDER STEP #4. THE YES COLUMN SHOULD READ GO TO STEP #5.

* 1997 T-SERIES AND THE C-SERIES OF THE MEDIUM DUTY TRUCKS AND THE B-7 CHASSIS. - THE STEP #5 ACTION COLUMN ITEM #1 IN TABLE DTC 34 IS INCORRECT. THE ITEM #1 SHOULD NOW STATE TURN ON THE IGNITION.

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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.