Conventional Speed Control: Notes
DESCRIPTION
The Cruise Control system is comprised of the following components:
| 1. | Refer to POWERTRAIN CONTROL MODULE (PCM) . |
| 2. | Refer to BODY CONTROL MODULE (BCM) . |
| 3. | Refer to CRUISE CONTROL SWITCH MODULE (CSWC) - This is the speed control switch pod located on the right steering wheel spoke. |
| 4. | Refer to STEERING COLUMN CONTROL MODULE (SCCM) . |
| 5. | Refer to INSTRUMENT PANEL CLUSTER (IPC) . |
| 6. | Refer to ANTI-LOCK BRAKE SYSTEM (ABS) MODULE . |
| - | Refer to TRANSMISSION CONTROL MODULE (TCM) - Integral to the Automatic Transmission (ATX). |
OPERATION
Cruise Control
- The driver of the vehicle presses any of the cruise control specific buttons.
- The cruise control switch transits the request over the Local Interface Network (LIN) bus to the SCCM.
- The SCCM transmits this information over the Controller Area Network-Chassis (CAN-C) bus to the PCM.
- The PCM manages the algorithm in order to keep the vehicle speed set by the driver.
Active Speed Limiter
Active Speed Limiter is a function that allows the driver to set the vehicle speed limit. This function is set by the driver by interfacing with the CSWC button interface. The limiter function is active when the speed of the vehicle is equal to the limitation set point designated by the driver. If the driver exceeds this designated set point, the driver will be warned through audio and visual messages on the IPC. The driver is able to override the limiter function by pressing the accelerator pedal to speed the vehicle beyond the designated set point.
It is important to note that any vehicle driving system utilizing active torque requests (such as braking, traction, or stability events) will take precedence over and inhibit the active speed limiter and cruise control functions. Active speed limiting and cruise control will operate again once the torque request has been honored.
Active speed limiter and Hill Descent Control (HDC) are mutually exclusive and can not be active at the same time.
Downhill Cruise Control Operation
This function helps minimize vehicle speed errors during a downhill cruise event by requesting a downshift from the transmission. This function is not enabled when the calibration to enable to the feature is turned OFF. Downhill cruise is entered when the following conditions are met:
- Calibration to enable downhill cruise in turned ON
- Cruise control is ON and in regulation mode
- Cruise control is not in override, resume or acceleration modes
In order for the PCM to request a downshift, all of the following conditions must be met:
- Vehicle acceleration is 0 kmh (0 mph)
- Current gear is greater than the allowed gear state based on vehicle speed
- Max gear requested is greater than the minimum allowed gear state based on vehicle speed
- Requested torque is less than the actual torque
Before requesting the downshift, the PCM will wait a calibrated amount of time of four seconds before taking any action. Once that delay has elapsed, the PCM will send the maximum gear to the transmission as a function of vehicle speed and the current engaged gear. When the downshift request is made and the TCM accepts the request, the PCM will continue to monitor for overspeed conditions. If conditions to enter downhill cruise control mode no longer exist, the PCM will request an upshift if conditions exist for at least four seconds. Upshift to a gear is dependent on the current gear and the vehicle speed.
If the customer performs a tap up, tap down, resume or deceleration maneuver while in downhill cruise control mode, the cruise control logic will act the same such that the set speed is modified according to button activation and the downhill cruise function will is frozen. Once cruise control is no longer responding to the customer requests, the downhill cruise function will then become active once again. If the customer presses the accelerator pedal at any time during downhill cruise control, the downhill cruise control feature will be exited.