Cruise control is a speed control system that maintains a desired vehicle speed under normal driving conditions at speeds above 40 km/h (25 mph). However, steep grades may cause variations in the selected speeds. The main components of
the cruise control system are:
| • | The cruise control module assembly |
| • | The cruise control switches |
| • | The cruise control release switch |
| • | The powertrain control module (PCM) |
| • | The stop lamp switch assembly |
| • | The vehicle speed sensor |
The cruise control system has the capability to adjust speeds and disengage the system based on the activation of the following cruise control switches:
The cruise control module controls the operation of the cruise control system. The cruise control module monitors the signal circuits of the cruise control switches. When the normally open cruise On/Off switch closes with a switch activation, the cruise
control modules detects a high voltage on the signal circuit. The cruise control module activates the cruise control system. The set/coast switch and the resume/accel switch will not operate the system when the cruise control module has not activated the
system based on the cruise control on/off switch signal circuit .
The cruise control module monitors the cruise control set/coast switch in order to determine when to capture and maintain the vehicle speed. The cruise control module monitors the vehicle speed signal circuit in order to determine the desired speed.
The PCM pulses the vehicle speed signal circuit at 4000 pulses per minute. After an initial set speed has been established, the cruise control module also uses the cruise control set/coast switch signal circuit in order to tap down the set speed when the
cruise control module detects a switch activation.
The cruise control module monitors the cruise control resume/accel switch signal circuit in order to determine when to resume the previous set speed. This feature only works within the same ignition cycle and as long as the cruise wasn't turned off
using the cruise control On/Off switch since the last cruise engagement. After the set speed has been resumed, the cruise control module also uses the cruise control resume/accel switch signal circuit in order to tap up the set speed when the cruise control
module detects a switch activation.
The cruise control module assembly has a controller and an electric stepper motor to vary the throttle in each different cruise control mode. Two components in the module assembly help to do this. The electronic controller and the electric stepper
motor. The controller monitors vehicle speed and operates the stepper motor. The stepper motor operates in response to the controller, to maintain the desired cruise speed. The electric stepper motor moves a strap that is attached to the cruise control
cable which moves the throttle linkage.
Cruise Control Engaged
The cruise control module grounds the cruise engaged signal circuit when cruise control is engaged. The powertrain control module (PCM) monitors the cruise engaged signal circuit in order to determine when the cruise control is engaged. The cruise control
module, cruise cancel signal circuit, is a circuit used by the PCM to inhibit cruise control when conditions inconsistent with cruise operation are present.
Cruise Control Disengaged
The cruise control release switch and stop lamp switch are used to disengage the cruise control. A release switch assembly and a stop lamp switch assembly are mounted on the brake pedal bracket . To disengage the system the driver presses the brake
pedal. The speed of the vehicle at brake actuation will be stored in the memory of the cruise module. The cruise control module uses that stored speed when the cruise control system operation is resumed.
Cruise Control Inhibited
The powertrain control module (PCM) determines when the vehicle operating conditions are not appropriate for cruise control operation. The PCM inhibits the cruise control operation when any of the following conditions occur:
| • | The vehicle speed is less than 40 km/h (25 mph). |
| • | The vehicle is in PARK, REVERSE, NEUTRAL, or 1st gear. |
| • | The engine RPM is high with fuel cut-off. |
| • | The vehicle speed is too high. |
| • | The battery is either overcharged or undercharged. |
| • | The antilock brake system/traction control system is active for more than 2 seconds |
When any of the conditions listed above are present, the PCM removes the ground from the cruise control inhibit signal circuit. The cruise control module monitors the cruise control inhibit circuit in order to disable the system. The PCM compares the
status of the cruise control inhibit signal circuit to the status of the cruise control engaged signal circuit. If the cruise control engaged signal circuit indicates that the cruise control module has cruise control engaged while the PCM is inhibiting cruise
control operation, the PCM sets a DTC.
Another feature, internal to the cruise control module is the lash learn feature. The cruise control module has the ability to learn and electronically compensate for up to 4 mm of lash in the non-adjustable cruise control cable. The cruise
control module maintains this adjustment and updates this information every 30 seconds.
