HARDSTART & STUMBLE, WITH MIL ON & POSS. HISTORY DTC'S. GMC Truck Yukon

SUBJECT: HARD START, STUMBLE, WITH MIL ON AND POSSIBLE HISTORY DTC'S OF P0251, P0370, P1216 (REFLASH WITH NEW CALIBRATION)

MODELS: 1997 CHEVROLET AND GMC C/K, G, P TRUCKS 1997 HUMMER (AM GENERAL) WITH 6.5L DIESEL ENGINES (VINS S, F--RPOS L56, L65, L65-CMT)

THIS BULLETIN IS BEING REVISED TO CHANGE SUBJECT/CONDITION INFORMATION.

CONDITION:

SOME OWNERS MAY EXPERIENCE A HARD START, OR STUMBLE WITH THE MIL ON. IN ADDITION, THE VEHICLE MAY HAVE HISTORY DTC'S OF P0251, P0370, AND P1216. THE CONDITIONS LISTED MAY BE INTERMITTENT AND MAY NOT BE REPEATABLE IN THE DEALERSHIP.

DO NOT REPLACE THE FUEL INJECTION PUMP FOR THIS CONDITION.

CAUSE:

CONDITION MAY BE CAUSED BY EITHER AIR IN THE FUEL SYSTEM OR CONTAMINATION, SUCH AS WATER. IF AIR OR WATER ARE DRAWN THROUGH THE FUEL INJECTION PUMP, FALSE DTC'S MAY BE SET IN ADDITION TO CREATING DRIVEABILITY CONCERNS. AIR CAN ENTER THE FUEL SYSTEM THROUGH EITHER POOR FUEL LINE CONNECTIONS, THE FUEL TANK PICKUP TUBE IF THE TANK IS BELOW APPROXIMATELY 1/8 FULL AND HARD ACCELERATION OR TURNING MANEUVERS ARE PERFORMED, OR BY ALLOWING THE VEHICLE TO COMPLETELY RUN OUT OF FUEL. WATER AND OTHER FUEL SYSTEM CONTAMINATION IS USUALLY THE RESULT OF THE CUSTOMER'S SOURCE OF FUEL.

CORRECTION:

ALWAYS PERFORM NORMAL DIAGNOSTICS INCLUDING AN ON BOARD DIAGNOSTICS (OBD) SYSTEM CHECK PRIOR TO MAKING ANY REPAIRS. CHECK THE FUEL SYSTEM FOR WATER OR OTHER CONTAMINATION. IF WATER IS DETECTED, REFER TO THE ENGINE CONTROLS SECTION OF THE APPROPRIATE TRUCK SERVICE MANUAL FOR THE PROPER PROCEDURE TO DRAIN AND CLEAN THE ENTIRE SYSTEM. CHECK FOR AIR USING THE DIAGNOSTIC PROCEDURE CALLED THE FUEL SYSTEM AIR LEAK TEST. IT IS LISTED UNDER THE FUEL SUPPLY SYSTEM CHECK IN THE ENGINE CONTROLS SECTION OF THE APPROPRIATE TRUCK SERVICE MANUAL. REFER TO BULLETIN 67-65-39 (SECTION 6E-ENGINE-FUEL AND EMISSION) FOR FURTHER INFORMATION. IF NORMAL DIAGNOSTICS DO NOT LEAD TO PROBLEM RESOLUTION, CHECK THE VEHICLE FOR THE CALIBRATION IDENTIFICATION NUMBER USING A TECH 2 SCAN TOOL. NEXT CHECK THE TECHLINE TERMINAL FOR AN UPDATED CALIBRATION NUMBER. REFLASH WITH THE UPDATED CALIBRATION IF THE CURRENT VEHICLE CALIBRATION IS NOT THE NEWEST ONE LISTED IN YOUR TERMINAL. REFER TO THE APPROPRIATE SERVICE MANUAL OR TECHLINE USERS GUIDE FOR DETAILED INSTRUCTIONS ON THE REPROGRAMMING PROCEDURE.

WARRANTY INFORMATION:

FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OPERATION - J6355 DESCRIPTION - REPROGRAMMING PROM LABOR TIME - USE PUBLISHED LABOR OPERATION TIME.

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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.