OVERVIEW
The speed control system maintains a set speed selected by the driver until operation is suspended or cancelled by a further input from the driver and is controlled by the ECM.
The speed control system comprises the following components
- A set +/- switch
- A RESUME switch
- A CANCEL switch.
The system also uses the following
- The ECM
- The stoplamp switch.
- The APP sensor
The ECM controls the set speed by modifying engine speed/torque and requesting gear changes from the transmission (automatic variants only).
The speed control system also uses inputs from the brake pedal switch, the APP sensor, the ECM and the ABS control module.
The speed control is operated by the driver using only the steering wheel switches. When speed is active, the ECM regulates the PWM signals to the fuel injectors to adjust the fuel supply as required to maintain the set speed.
During speed control operation, the ECM controls vehicle speed by adjusting fuel injection duration and timing. When the accelerator pedal is pressed with speed control active, the ECM outputs a calculated throttle angle signal in place of the actual throttle angle signals produced by the APP sensor. The calculated throttle angle is derived from fuel demand.
Scheme 2
| Item Number | Description |
|---|---|
| 1 | Set target speed/increase speed |
| 2 | Set target speed/decrease speed |
| 3 | Resume set speed |
| 4 | Speed control suspend. |
The speed control switches are located on the LH side of the steering wheel. The switches are connected via fly leads directly to the clock spring. All the speed control switches are non-latching momentary rocker switches. The minimum set speed is 18 mph (30 (km/h). Speed control is automatically suspended if the vehicle speed falls below 15 mph (24 km/h).
The speed control switches are resistive ladder type switches. There are three rocker switches associated with speed control, two of which are for adaptive speed control (where specified). The switches vary the resistance of a signal voltage sent to the ECM. The switches receive a 5 volt reference supply. The ECM measures the returned voltage to determine which switch has been pressed.
PRINCIPLES OF OPERATION
For a detailed description of the speed control system, refer to the relevant Description and Operation. Refer to SPEED CONTROL - DESCRIPTION & OPERATION (3.2L) .