Optimized Idle®

p3 dm 11.04.001

Optimized Idle reduces engine idle time by running the engine only when required. Optimized Idle automatically shuts down and restarts the engine as needed to ensure engine oil temperature remains within factory preset limits, the batteries stay charged, and cab/sleeper temperature remains at the thermostat setting. The benefits of the system include reduced engine idle time, fuel savings, reduction of exhaust emissions and noise, increased starter and engine life, and reduced chance of dead batteries.

Vehicles equipped with Optimized Idle have a label on the dash, and a telltale (OPT IDLE) in the ICU. See Fig. for the dash label detail. If equipped, a thermostat is located above the sleeper bunk. See Fig..

Fig. 1, Optimized Idle Dash Label

  1. Down Arrow Button

  2. Up Arrow Button

  3. Upper/Lower Temperature Icon

  4. Temperature Display

  5. Degrees Fahrenheit Indicator

  6. MODE Button

  7. Cooling Icon

  8. Cool/Heat Selection Button

  9. Heating Icon

  10. Degrees Celsius Indicator

Fig. 2, Optimized Idle Thermostat

Optimized Idle operates in two modes:

  • Engine mode: Keeps the battery charged and engine oil temperature between 60 and 104°F (16 to 40°C).

  • Thermostat mode (activated when the optional thermostat is turned on): Keeps the cab and sleeper at a constant preset temperature, in addition to all functions available in engine mode.

Thermostat mode controls the set point, which is the desired temperature of the cab and sleeper, and the comfort zone, which is the allowed temperature deviation from the set point before the engine starts.

The thermostat display defaults to show the temperature of the sleeper, but changes accordingly as the buttons are pressed.

The button functions are as follows:

  • Up arrow: Increases the set point and comfort zone (allowed temperature variation).

  • Down arrow: Decreases the set point and comfort zone.

  • Cool/Heat: Sets either cooling or heating operation.

  • MODE: Scrolls through the various functions. It can also be used to set desired temperature values.

If a vehicle has Optimized Idle, the following functions will not operate with the key in accessory mode. Optimized Idle may also turn these functions off to reduce stress on the batteries.

  • Cab climate control fan

  • Sleeper climate control fan

  • Mirror heat

  • Fuel/water separator heat

  • Seat heat

  • Advertising light

  • Auxiliary circulation fan (windshield)

  • Air dryer

  1. To activate Optimized Idle (engine mode):
    1. Set the parking brake.
    2. If it is open, close and secure the hood.
    3. Start the engine and let it idle.
    4. Put the transmission in neutral.
    5. Turn on the cruise control.
      The OPT IDLE lamp will blink, indicating that Optimized Idle is active. The system is now in engine mode and after an initial phase, in which the idle speeds up to 1000 rpm, the engine will stop and start automatically to keep the battery charged and the engine oil warm.

      Important: The cruise control must be turned on once the engine is idling. If it was previously turned on, turn the cruise control off, then turn it on again.
    6. Activate thermostat mode, if equipped.

      Note: When the system is in thermostat mode, it is also in engine mode. It will continue to operate in engine mode even if thermostat mode is turned off.
        1. With the system in engine mode, set the cab and sleeper heater or air conditioner controls to the highest setting.
        2. Turn on the thermostat by touching any of the four buttons. See Fig..
          The display will flash the current sleeper temperature and the previous mode (cooling or heating) selected. If the cab needs to be cooled or heated, the cool/heat icon will flash.
        3. Choose either cool or heat by pressing the Cool/Heat button. Make sure the selection matches that of the cab controls.

          Important: If the heat or cool selection of the thermostat does not match that of the cab controls, the system will idle and cycle excessively.
          1. Select Fahrenheit or Celsius by pressing and holding the MODE button until either the "F" or "C" is displayed.
          2. Select the temperature set point by pressing the up or down arrows, as applicable. Holding the button will cause the display to scroll up or down rapidly. When the desired set point is displayed, release the button. The set point is stored in memory.
          3. Select the temperature comfort zone by pressing the MODE button until the upper and lower temperature limit icon is displayed. Then use the up or down arrow to select one of the three comfort zones: 4°F (2°C), 7°F (4°C), or 10°F (6°C).
        4. To deactivate thermostat mode and return to just engine mode, press and hold the MODE button for three seconds.
        5. To shut down Optimized Idle completely, either turn off the ignition or use the drive away feature.
          The drive away feature allows the use of all the engine features. Use the drive away feature as follows:
          1. If the engine is running: Release the parking brakes or put the transmission in gear.
            If the engine is not running: Start the engine. Release the parking brakes or put the transmission into gear.
          2. Let the engine return to base idle. The active light will turn off. Optimized Idle is now disabled.
        Note:
        Parent topic: Optional Engine Systems
        Document Number: 0000113546
        Manual Publication Date: 2025-02-11
        Topic Publication Date: 2024-05-06