Principles of Operation
Cruise Control
Principles of Operation
The cruise control system is controlled by the PCM. The cruise control system is designed to maintain a selected vehicle speed between 40 km/h (25 mph) and the maximum limited vehicle speed. The cruise control system is controlled by the cruise control switches (ON/OFF, SET+, SET-, and CNCL/RSM) that are integrated into the LH steering wheel switch, and by the brake pedal. The cruise control switches are hardwired to the Steering Column Control Module (SCCM). The SCCM (Steering Column Control Module) sends High Speed Controller Area Network (HS-CAN) messages to the PCM to control the cruise control system.
The clockspring provides the electrical interface between the steering column wiring and the cruise control switches in the steering wheel.
The cruise control functions include:
- turning on the cruise control system.
- setting and maintaining the desired vehicle speed.
- accelerating the vehicle speed.
- coasting down to a lower speed.
- resuming the prior vehicle speed.
- turning off the cruise control system.
Pressing and releasing the ON/OFF switch turns the cruise control system on. The cruise control indicator located in the Instrument Panel Cluster (IPC) illuminates amber to indicate the cruise control system is in standby mode. Pressing and releasing the SET+ or SET- switch while the vehicle is traveling at the desired speed activates the cruise control system. The cruise control indicator illuminates green to indicate the cruise control system is active.
Tapping the SET+ or the SET- switch while in the set mode, increases or decreases the maintained vehicle speed by 1.6 km/h (1 mph) per tap. If the respective switch is pressed and held, the vehicle speed continues to accelerate or decelerate until the switch is released.
Pressing and releasing the ON/OFF switch, or turning the ignition switch to the OFF position, turns the cruise control system off. Applying the brake pedal or pressing the CNCL/RSM switch while the cruise control system is active, puts the cruise control system into the standby mode. Pressing the CNCL/RSM switch when the cruise control system is in the standby mode causes the vehicle to accelerate to the last set speed. Resume does not function if the ON/OFF switch is pressed, the ignition switch is in the OFF position, or if the current vehicle speed is below the minimum operational speed.
The cruise control deactivator switch is an additional safety feature. Normally, when the brake pedal is applied, an electrical signal from the stoplamp circuit to the PCM deactivates the system. Under increased brake pedal effort, the cruise control deactivator switch opens and removes the ground signal (3.7L, 5.0L, 6.2L engine) or reference voltage (3.5L engine) from the PCM input circuit, and the PCM commands the throttle body closed.
The inputs to the PCM are:
- Output Shaft Speed (OSS) sensor
- Digital Transmission Range (TR) sensor
- Cruise control switch(es) (networked from SCCM (Steering Column Control Module) )
- Cruise control deactivator switch (integral to the stoplamp switch)
- Stoplamp switch
- Accelerator Pedal Position (APP) sensor
- Vehicle speed (networked from ABS module)
The outputs of the PCM are:
- Cruise control indicator lamp request to the IPC (Instrument Panel Cluster)
- Throttle body
The vehicle speed is controlled by the PCM through the Electronic Throttle Control (ETC) subsystem.
In the event of an ON/OFF switch command or a deactivation request from the deactivator switch, the cruise control system carries out a deactivation and immediately returns the throttle to the idle position.
The cruise control system provides self-diagnostics. Cruise control is disabled anytime an error is detected in the system. No IPC (Instrument Panel Cluster) indicator or message center messages are displayed when faults occur. Fault codes are logged by the PCM or SCCM (Steering Column Control Module).
An ETC (Electronic Throttle Control) system fault also disables the cruise control system. In this case, an ETC (Electronic Throttle Control) system powertrain malfunction (wrench) warning indicator is displayed.
Additionally, the following conditions cause the cruise control system to deactivate:
- Transmission gear selector in a position other than D or OD
- Cruise control set speed is overridden with the accelerator pedal for a period longer than 5 minutes
- Vehicle speed loss from set speed of greater than 16 km/h (10 mph) occurs
- Vehicle speed falls below the minimum allowable limit of 40 km/h (25 mph)
- Cruise control switch pressed or stuck longer than 2 minutes
- ABS fault
Cruise Control Deactivation Event PIDs
The PCM has PIDs available, through the powertrain DataLogger, that show what caused the cruise control deactivation during the current key cycle. The PCM has 24 cruise control deactivation event PIDs, identified as CRUISEOFF_00 through 24. All deactivation events that occur during active cruise operation are listed in the event PID. Switching the ignition off will erase all recorded deactivation events. These PIDs display what caused the cruise control deactivation to trigger and can be a very useful tool when trying to identify the cause of a deactivation or non-activation trigger. The event PIDs displays the deactivation or non-activation trigger based on when the cruise control is turned on and the fault condition exist. If the cruise control system is turned on or off prior to or in advance to the triggering condition, the events PIDs may display inaccurate deactivation conditions. The event PIDs should be read when the conditions of deactivation or non-activation exist.