The cruise control system consists of the following components
- Cruise control switches
- Cruise control deactivator switch (integral to the stoplamp switch)
- Cruise control indicator
- PCM
- Electronically-controlled throttle body
- Clockspring
The cruise control system is controlled by the PCM. The cruise control system is designed to maintain a selected vehicle speed between 37 km/h (23 mph) and the maximum limited vehicle speed. The cruise control system is controlled by the steering wheel mounted switches (ON, OFF, SET+, SET-, and RESUME), and the brake pedal. The steering wheel mounted switches are hardwired to the PCM.
When a MyKey™ is used and the MyKey™ max speed limiter is turned on, the vehicle speed cannot be set to exceed 130 km/h (80 mph).
Principles of Operation
Note. The Smart Junction Box (SJB) is also known as the Generic Electronic Module (GEM).
Pressing and releasing the ON switch turns the cruise control system on. Pressing and releasing the SET+ or SET- switch while the vehicle is traveling at the desired speed activates the cruise control system.
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 button is pressed and held, the vehicle speed continues to accelerate or decelerate until the button is released.
Pressing and releasing the OFF switch, or switching the ignition switch to the OFF position, turns the cruise control system off. Pressing the brake pedal puts the cruise control system in the standby mode. Pressing the RESUME button 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 OFF button is pressed, the ignition switch is in the OFF position, or if the current vehicle speed is below the minimum operational speed.
Whenever the cruise control system is engaged and active, a cruise control indicator on the Instrument Cluster (IC) is illuminated.
The cruise control deactivator switch is provided as an additional safety feature. Normally, when the brake pedal is pressed, an electrical signal is sent from the stoplamp switch to the PCM and the SJB to deactivate the cruise control system. The SJB sends a message to the IC and the illuminated cruise control indicator is turned off. Under increased brake pedal effort, the deactivator switch opens and removes the voltage from the PCM input circuit, releasing the throttle.
The clockspring provides the electrical interface between the steering column wiring and the cruise control switches in the steering wheel.
The inputs to the PCM are
- Output Shaft Speed (OSS) sensor
- Cruise control switches
- Stoplamp switch
- Cruise control deactivator switch (integral to the stoplamp switch)
- SJB messages
The outputs of the PCM are
- Cruise control indicator lamp
- Throttle command
The throttle position is completely controlled by the PCM through the electronically-controlled throttle body. Cruise control electronics are contained entirely within the PCM.
When the cruise control system is active, the PCM corrects for deviations in the actual vehicle speed by proportionally moving the throttle plate. The PCM modulates the throttle to minimize error between actual vehicle speed and the desired speed.
The PCM strategy uses the throttle control for smooth accelerations.
The PCM sends a serial message over the Controller Area Network (CAN) to the IC whenever the cruise control indicator should be turned on or off.
In the event of an off command or a deactivation request from the deactivator switch, the cruise control system carries out a hard deactivation and immediately returns the throttle to the idle position.
The cruise control system provides self-diagnostics. The cruise control system is disabled anytime an error is detected in the system. No IC indicator or message center messages are displayed when faults occur. Fault codes are logged by the PCM.
An Electronic Throttle Control (ETC) system fault also causes the cruise control system to be disabled. In this case, an ETC system warning indicator or message center message is displayed.
Additionally, the following conditions cause the cruise control system to deactivate
- Transmission gear selector is put into any 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 37 km/h (23 mph)
- Cruise control switch is pressed or stuck longer than 2 minutes
Normal Operation
A reference voltage is sent from the PCM to the steering wheel cruise control switches. When a switch is pressed, the voltage is routed through a specific resistor value for each function. The PCM provides the ground for the reference voltage to determine which control input function has been selected. When the brake pedal is applied, the PCM deactivates the cruise control, if engaged. The cruise control deactivator switch (integral to the stoplamp switch) removes the voltage signal to the PCM when the brake pedal is applied firmly. This is a redundant signal to the PCM.
This pinpoint test is intended to diagnose the following
- Wiring, terminals or connectors
- PCM not configured for cruise control
- Cruise control switch
- Digital Transmission Range (TR) sensor
- Vehicle Speed Sensor (VSS)
- PCM
- ABS module fault
When the brake pedal is applied, the stoplamp switch closes and sends voltage to the PCM to deactivate the cruise control, if engaged. The cruise control deactivator switch (integral to the stoplamp switch) removes the voltage signal to the PCM when the brake pedal is applied firmly and passes the cruise control deactivator switch point. This is a redundant signal to the PCM.
- DTC P1703 (Brake Switch Out Of Self Test Range) - sets when there is an open or short in the deactivator switch circuits or when there is an open or short in the stoplamp circuits.
- Stoplamps system concern
- Wiring, terminals or connectors
- Cruise control deactivator switch (integral to the stoplamp switch)
- ABS module
- PCM
Voltage is sent from the PCM to the cruise control switch. When a switch is pressed, the voltage is routed through a specific resistor value for each function and the PCM grounds the reference voltage. The PCM uses this reference voltage to determine which cruise control input function has been selected.
- DTC P0579 (Cruise Control Multifunction Input A Circuit Range/Performance) - may set when the cruise control switch circuits are open, shorted to voltage or ground.
- DTC P0581 (Cruise Control Multi-Function Input A Circuit High) - sets when the cruise control switch circuits are open or shorted to voltage.
This pinpoint test is intended to diagnose the following
- Wiring, terminals or connectors
- Clockspring
- Cruise control switch
- PCM