INFO. ON ENGINE OVERHEAT PROTECTION FEATURE. GMC Truck GMC Suburban

SUBJECT: INFORMATION ON ENGINE OVERHEAT PROTECTION FEATURE AND POSSIBLE LOSS OF POWER WHEN TRAILERING

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

CUSTOMERS MAY EXPERIENCE REDUCED ENGINE POWER WHEN OPERATING THE VEHICLE WITH HOT COOLANT TEMPERATURE (210 DEGREES FAHRENHEIT AND ABOVE). DTCS ARE NOT SET AND THE VEHICLE RUNS FINE WHEN OPERATING AT NORMAL COOLANT TEMPERATURES. REDUCED ENGINE POWER IS MOST PREVALENT WHEN PULLING LOADS UP GRADES OR DURING HOT WEATHER.

THE FUEL SYSTEM HAS AN ENGINE PROTECTION SYSTEM THAT ATTEMPTS TO KEEP THE ENGINE FROM OVERHEATING. BY REDUCING THE AMOUNT OF FUEL DELIVERED TO THE CYLINDERS, ENGINE POWER IS REDUCED AS IS THE HEAT LOAD TO THE COOLING SYSTEM. AN ENGINE PROTECTION FEATURE BUILT INTO THE PCM IS ACTIVATED WHEN COOLANT TEMPERATURE REACHES APPROXIMATELY 210 DEGREES FAHRENHEIT. THE PCM WILL COMMAND THE FUEL INJECTOR PUMP TO REDUCE THE AMOUNT OF FUEL DELIVERED TO THE ENGINE CYLINDERS. THE HOTTER THE COOLANT BECOMES, THE MORE THE FUEL DELIVERY IS REDUCED. NO DTCS ARE SET WHEN THE PCM ACTIVATES THE ENGINE PROTECTION FEATURE, AS IT IS NORMAL OPERATION.

VEHICLES SHOULD BE CHECKED AND INSPECTED IF CONSTANTLY OPERATING IN THE ENGINE OVERHEAT PROTECTION ZONE. CONSULT THE SERVICE MANUAL FOR REASONS THAT MAY CAUSE UNUSUAL ENGINE TEMPERATURE PROBLEMS. THE REDUCTION OF POWER WHEN THE ENGINE OPERATES ABOVE 210 DEGREES FAHRENHEIT IS NORMAL OPERATION OF THIS PRODUCT. ALL VEHICLES WILL EXPERIENCE LOSS OF POWER DUE TO THE ENGINE OVERHEAT PROTECTION FEATURE WHEN OPERATED UP HILLS WITH HEAVY LOADS IN HOT WEATHER. CUSTOMERS NEED TO BE INFORMED OF THE ENGINE OVERHEAT PROTECTION FEATURE. WHEN THE FAN CLUTCH IS FULLY ENGAGED AND THE PCM HAS REDUCED THE MAXIMUM CALIBRATED AMOUNT OF FUEL, THE ENGINE COULD LOSE UP TO 25 PERCENT OF POWER.

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Object Number: 95111 Size: SH

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.