Dodge Cummins Diesel Forum banner
1 - 1 of 1 Posts

2,595 Posts
Extended idle operation, especially in cold weather, can lead to stuck valves and bent push-tubes due to insufficient cylinder heat. This allows varnishes/oils to condense on the exhaust valve stems, leading to stuck valves, and damaged valve train components. A new software feature, enabled or disabled through the DRB III (See instructions under Repair Procedure), reduces the chance of valve sticking and improves cab heat warm-up time.

Once enabled, idle speed will slowly ramp up from 800 rpm to 1200 rpm when ALL of the following conditions are met:

1. Intake Manifold Temperature less than 0°C (32°F) and,
2. Coolant Temp is less than 60°C (140°F) and,
3. The Transmission is in Neutral or Park and,
4. The Service Brake pedal is not depressed and,
5. Throttle = 0% and,
6. Vehicle Speed = 0 mph

Additionally, if Intake Manifold Temperature (IMT) is less than -9°C (15°F), and all of the parameters above are met, three of the cylinders will be shut off upon reaching 1200 rpm, creating a slight change in engine sound which is normal. This allows the engine to create increased heat in the cooling system, allowing more rapid engine warm up and cab heating.

Both features will automatically disable when one of the following occurs:

1. The Automatic Transmission is placed in gear (forward or reverse) or,
2. The Service Brake pedal is depressed or,
3. Throttle position is greater than 0% or,
4. Vehicle Speed is greater than 0 mph or,
5. Coolant Temperature is greater than 79°C (175°F).

Engine speed will return to normal operation at 800 rpm. If the engine continues to idle and coolant temperature is at or below 60°C (140°'F), the feature will reenable. In order to operate properly, the Accelerator Pedal Position Sensor (APPS) must stay at idle.


Use of the 110V block heater will not allow the feature to function after an overnight soak. If the vehicle is left idling, without use of the block heater, 1200 rpm operation will begin when the intake temperature drops below O°C (32°F) and coolant is less than 60°C (140°F).

Now, some things to remember about this... if the ambient air temp is right at or near 15°F, the 3 cylinder might night activate for these reasons; first, the grid heater is going to pre-heat, and continue heating, the incoming air before it reaches the IAT... second, it takes 1 minute for the 3 cylinder to activate(I timed it), in that time, some engine heat will undoubtedly be created which may affect the IAT reading. If it's not activating and it's 10°F or less, you might have a bad IAT.

When my truck still cared that it had an ECM attached to it, the high-idle was very finicky.. the overnights had to sustain those below 32°F temps for several hours to really get things working. I suspect I had an IAT issue though.
1 - 1 of 1 Posts