INFO - DIAGNOSING VARIOUS DIESEL DRIVEABILITY CONDITIONS. GMC Truck Yukon

SUBJECT: INFORMATION - DIAGNOSING VARIOUS DIESEL DRIVEABILITY CONDITIONS

MODELS: 1994-1998 CHEVROLET AND GMC C/K, G, P MODELS WITH 6.5L DIESEL ENGINE (VINS P, S, Y, F - RPOS L49, L56, L57, L65)

SOME DIESEL EQUIPPED VEHICLES MAY EXHIBIT VARIOUS DRIVEABILITY CONDITIONS SUCH AS POOR START, STALL, EXHAUST SMOKE, HESITATION, OR POOR PERFORMANCE, YET THE VEHICLE DOES NOT READILY EXHIBIT THE CAUSE WHEN EVALUATED IN THE DEALERSHIP. IN ADDITION, THE PCM MAY NOT HAVE ANY DIAGNOSTIC TROUBLE CODES (DTC'S) STORED IN HISTORY.

SOMETIMES THE ROOT CAUSE OF CONDITIONS ARE NOT EASILY DIAGNOSED IN THE DEALERSHIP SERVICE DEPARTMENT, AND OCCASIONALLY, NO DTC'S ARE SET TO ASSIST IN DIAGNOSIS. THESE CONDITIONS MAY BE CAUSED BY OTHER RELATED VEHICLE SYSTEMS SUCH AS FUEL, EXHAUST, OR EVEN LACK OF PROPER MAINTENANCE (SUCH AS RESTRICTED AIR FILTERS ETC.)

IF A DRIVEABILITY CONCERN IS NOTED BY THE VEHICLE OWNER, THE DEALERSHIP TECHNICIAN SHOULD USE A SYSTEMATIC OR STRATEGY BASED DIAGNOSTIC METHOD TO EVALUATE THE CONDITION. A POWERTRAIN ON BOARD DIAGNOSTIC (OBD) SYSTEM CHECK SHOULD BE PERFORMED PRIOR TO ANY OTHER REPAIR. IF THE POWERTRAIN CONTROL MODULE (PCM) IS OPERATING PROPERLY, AND NO DTC'S ARE STORED, REFER TO THE ENGINE CONTROLS "SYMPTOM" SECTION OF THE APPROPRIATE SERVICE MANUAL. FOR EXAMPLE, WITH THE 1998 C/K MODEL, THE SYMPTOM SECTION IS IN BOOK 4, SECTION 6, STARTING ON PAGE 2559. INCLUDED IN THIS BULLETIN, FOR YOUR REFERENCE, IS A DIAGNOSTIC WORKSHEET TO ASSIST IN YOUR EVALUATION OF AN OWNER CONCERN. IT IS TO BE USED IN CONJUNCTION WITH THE APPROPRIATE SERVICE MANUAL AS A DIAGNOSTIC AID.

FIGURES: 0 ATTACHMENTS: 2

Object Number: 484445 Size: FS

Object Number: 484447 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.