Engine - Loss of Power When Warm/Pulling Loads
File in Section: 6E - Engine Fuel & EmissionBulletin No.: 47-63-03
Date: September, 1994
Subject:
Engine Overheat Protection Feature and Possible Loss of Power when Pulling Loads
Models:
1994 Chevrolet and GMC Truck C/K Models 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°F 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°F. 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°F 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% of power.