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Cruise Control Operation on CUMMINS Engines (On-Highway Trucks)

Cruise Control - ISC / Transit Bus ISL8.3

Figure 1.1 - Cruise Control On/Off and Set/Resume Switch


#Feature Description
Cruise Control provides the driver with foot-off-throttle cruise operation, with the ability to adjust and maintain a desired road speed. Cruise Control and its capabilities vary according to its operational mode.

Two switches are used to operate this feature (refer to Figure 1.1 above):
  • The Cruise Control On/Off switch enables the operator to turn Cruise Control ON or OFF.
  • The Set/Resume-Coast/Accelerate switch enables the driver to set and resume Cruise Control. 

#Operational Modes
Three operational modes are possible, depending on switch settings and operating conditions:
  • Off - Cruise Control does not affect engine operation, and it cannot be activated. The Cruise Control On/Off switch is OFF.
  • Standby - The Cruise Control On/Off switch is ON, but Cruise Control has been deactivated and does not affect engine operation. Cruise Control remains on standby when the Cruise Control On/Off switch is initially placed ON until activation is requested by the driver using the Cruise Set/Resume switch. The driver can either set a desired speed or resume a desired speed. Activation is possible only when all of the following conditions are met:
    • Vehicle speed is not below 30 mph.
    • Engine speed is not at idle.
    • Brake pedal is not depressed.
    • Clutch pedal is not depressed.
    • A vehicle speed sensor fault is not present.
  • Active - Cruise Control is currently controlling engine fueling to maintain the desired road speed. Once activated, a Cruise Control reference speed is calculated by using information for the Cruise Control Maximum Speed, Driver Reward's reward speed, and the Cruise Control Set Speed. Cruise Control maintains vehicle speed at the Cruise Control Set Speed unless an interaction occurs with any one of the following: maximum torque curve, programmable droops, accelerator, or maximum vehicle speed (road speed governor limit).
Cruise Control cannot achieve vehicle speeds that require fueling that exceeds the maximum torque curve of the engine. The maximum torque curve is the maximum fueling allowed at an engine speed versus rpm for the horsepower rating of the engine.

#Adjustable Parameters
Figure 1.2 - Cruise Control/ Switch Setup
Cruise Control - Select the feature name to enable or disable the feature using the dropdown list in the ECM Value column.

Cruise Control Auto-Resume - This parameter allows the operator to resume to the cruise control set speed without pushing the Cruise Resume switch on the dash after the clutch has been pressed and released.

Cruise Control Lower Droop - This parameter sets the maximum vehicle speed for Cruise Control Lower Droop. A lower droop increases vehicle speed above the Cruise Control reference speed under light engine loads. A greater droop can result in better fuel economy in hilly or rolling terrain. A lesser droop provides better speed control. The recommended setting is 2 MPH.

Cruise Control Save Set Speed - When enabled, the Cruise Control speed established prior to shutdown can be resumed after the next restart using the resume function of the Cruise Set/Resume switch. When disabled, the resume function is inoperative until an adjustable Cruise Control speed has been established using the Set function.

Cruise Control Upper Drop - This parameter sets the maximum vehicle speed for Cruise Control Upper Droop. An upper droop decreases vehicle speed below the Cruise Control reference speed under heavy engine loads. A greater droop can result in better fuel economy in hilly or rolling terrain. A lesser droop provides better speed control. The recommended setting is 0 MPH.

Maximum Cruise Control Speed - The upper limit of the Cruise Control speed, unless Driver Reward is active. If Driver Reward is active, the upper limit is the sum of maximum Cruise Control Maximum Speed and Driver Reward's reward speed. The recommended setting is 62 MPH.

#Cruise Control Switch Setup
This feature is used to set the configuration of the Cruise Control set/resume switch. This feature reserves the switch throw for the accelerate and coast functions of the cruise set/resume switch.
Figure 1.3 - Cruise Switch Setup
Cruise Control Switch Setup - Select the feature name to enable or disable the feature using the dropdown list in the ECM Value column.

Switch Setup - Sets the function of the switch throw. Set/Accelerate is the up position and Resume/
Coast in the down position. Either this choice or the Set/Coast switch usage can be selected.

#Adaptive Cruise
This feature is a Cruise Control enhancement and driver convenience. When Adaptive Cruise is enabled, the adaptive cruise controller commands the ECM to reduce engine speed in order to maintain a minimum distance when following vehicles while Cruise Control is activated. If the following distance continues to decrease, the controller sends another command to the ECM to engage the engine retarder - typically the engine brakes, if installed on the engine - to further reduce engine speed.

Adaptive Cruise has two recovery modes that either allow or prohibit the use of standard Cruise Control in the event of an Adaptive Cruise system failure. Fault code 784, "Loss of Communication with Adaptive Cruise Control," is logged when a failure occurs.
Figure 1.4 - Adaptive Cruise (Disable)
Adaptive Cruise - Select the feature name to enable or disable the feature using the dropdown list in the ECM Value column.

Adaptive Cruise Recovery - Select to enable or disable Recovery mode using the dropdown list in the ECM Value column:
-If enabled, standard Cruise Control can be used in the event of an Adaptive Cruise system failure. 
-If disabled, standard Cruise Control can not be used in the event of an Adaptive Cruise system failure.

#Interaction with other Features and Parameters
Driver Reward - If the Driver Reward feature is enabled, Cruise Control may allow vehicle cruise speeds higher than the maximum Cruise Control speed. Cruise Control compares the Cruise Control Set Speed and the Driver Reward cruise speed, and the lesser of the two is used as the Cruise Control speed.
Figure 1.5 - Driver Reward (Disable)

Engine Brakes - 
Cruise Control Activation can be used to apply the engine brakes during cruise control use. Engine braking effort is determined by vehicle speed, the Cruise Control reference speed, Cruise Control speed for initial engine brake, and Cruise Control speed for maximum engine brake. In order for the Cruise Control to activate engine brakes, Engine Brake must be enabled, and all engine brake activation conditions must be met. If vehicle speed exceeds the Cruise Control reference speed for initial engine brake, Cruise Control will request the engine brakes to activate. If all requirements are met, the engine brakes will be applied at the minimum level.
Figure 1.6 - Engine Brake Control
If vehicle speed exceeds the Cruise Control reference speed for maximum engine brake, the engine brakes will be applied at their maximum level. Engine brakes will not increase beyond the level set by the engine brake level switch. Engine brakes will automatically deactivate as vehicle speed approaches the Cruise Control reference speed.

Gear Down Protection - Cruise Control Auto-Resume automatically deactivates and reactivates during Top 2 and manual shifts.
Figure 1.7 - Gear Down Protection (Disable)
→When Top 2 performs a shift, Cruise Control automatically deactivates and reactivates.
→When a manual shift is performed, Cruise Control deactivates when the clutch is depressed. It will automatically reactivate after the ECM detects an out-of-gear condition and the in-gear condition resumes in a different gear than the previous gear. 

Road Speed Governor Override - Depending on the status Gear-Down Protection, Cruise Control may or may not be able to cruise at vehicle speeds greater than the road speed governor's RSG reference speed. If Gear-Down Protection is active, the Cruise Control governor cannot exceed the road speed governor's RSG reference speed. If Gear-Down Protection is not active, the Cruise Control governor may cruise at speeds higher than road speed governor's RSG reference speed - up to a maximum vehicle speed.

Maximum Accelerator Vehicle Speed Limit - The accelerator can be used to increase vehicle speed temporarily above the Cruise Control set speed but below the global maximum vehicle speed. When the accelerator is released, Cruise Control automatically resumes the Cruise Control Set Speed.

Vehicle Speed - If the Vehicle Speed Sensor Type is set to None and Cruise Control is then disabled, you can not re-enable Cruise Control until the Vehicle Speed Sensor Type is changed to a type other than None.
Figure 1.8 - Vehicle Speed


#Additional Note:
a). Cruise Control On/Off Switch
→On/Off Signal, ECM OEM Connector: 06
→On/Off Return, ECM OEM Connector: 34
b). Cruise Control Set/Resume Switch
→Increment Signal, ECM OEM Connector: 24
→Decrement Signal, ECM OEM Connector: 25 








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