6.7L Cummins Forum

Dependent upon engine coolant temperature, the Engine Control Module (ECM) will
temporarily delay (limit) the maximum engine speed when the vehicle is not moving. For
automatic transmission equipped vehicles, the maximum engine speed is temporarily
delayed when the vehicle speed is less than one mph, and when the transmission selector
is in either the neutral or park position. For manual transmission equipped vehicles, the
maximum engine speed is temporarily delayed when the vehicle speed is less than one
mph. This ECM feature is used to protect the engine turbocharger.
By temporarily limiting the vehicle engine speed, the shaft speed of the engine
turbocharger is controlled to a low speed. This delay in maximum engine and
turbo-charger shaft speed allows for sufficient oil lubrication to the turbocharger shaft
bearings. Satisfactory oil lubrication of the turbocharger shaft bearings is important for long
term turbocharger durability.
The maximum engine speed for the 5.9L engine is temporarily limited to 1,600 RPM's
when the above conditions are met. The 6.7L engine speed is temporarily limited to 1,200
RPM's when the above conditions are met. The length of time that the maximum engine
speed is temporarily limited is dependent upon engine coolant temperature. Refer to the
table to determine the amount of Time Delay.