3 Cylinder High Idle Feature
This feature was introduced in the last quarter of 2001 for 1998 1/2 to 2002 Dodge Rams with the 24 valve Cummins 5.9L engine. The reason for its release is to protect the engine from low cylinder temperatures assosicated with extended idle times in cold weather. Eventually leading to a stuck valve which can contact the piston and cause extensive damage. In addition to protecting the engine an added side effect is much faster engine warm-up times. Through the use of a Chrysler DRB III this option can be enabled or disabled depending on the customers needs.
How it works:
There are two stages to this program. The first is a high idle feature that will ramp engine RPM's up to 1200 RPM when the intake manifold temperature is below 0 degrees celcius, the coolant temperature below 60 degrees celcius, the transmision in neutral or park, with the vehicle not moving, and neither the throttle nor brake pedals depressed.
The second stage is the same as above with the exception of the intake air temperature falling below -9 degrees celcius. With this criteria met once the engine reaches 1200 RPM three cylinder will be turned off. Unlike a high idle this actually places a load on the engine. The load can be as much as 15% and increase the exhaust gas temperatures up to 400 degrees fahrenheit over a basic idle. Once the three cylinders have been turned off the engine tone will change, this is completely normal.