Suspension Control ( Automatic - Electronic ): Description and Operation

SYSTEM DESCRIPTION:
The computer command ride (CCR) system controls the vehicle's ride firmness by controlling an actuator in each of the four struts to increase ride firmness as speed increases. The three damping modes are comfort, normal and sport. Damping mode selection is controlled by the CCR controller according to vehicle speed conditions, vehicle accelerometer input, and any error conditions which may exist.

Computer Command Ride (CCR) Controller
The CCR controller is a computer that controls and monitors the system. Located on a bracket under the driver's seat, the CCR controller receives speed and accelerometer inputs and determines the optimum mode strut valving for current operating conditions. The controller also monitors feedback signals from the struts to determine proper system operation. If the controller receives an incorrect feedback signal, a diagnostic trouble code is set in the CCR controller and the fault indicator (a light emitting diode [LED] on the CCR controller) lights. To aid in diagnosing the system. the fault indicator flashes diagnostic trouble codes when the CCR controller's diagnostic enable circuit is grounded.

Struts
Each strut contains an electrical actuator that rotates a selector valve to a specific location commanded by the CCR controller. The selector valve contains different sized orifices which increase or decrease the strut's damping rate to control ride firmness.

Vehicle Speed Input
The powertrain control module (PCM) supplies a speed input signal to the CCR controller. The CCR controller uses this signal to determine ride firmness. The ride firmness is selected according to the following speed conditions:

^ Speed increasing and below 8 mph (Stationary) - sport mode.
^ Speed Increasing and between 8 mph and 32 mph - sport mode.
^ Speed Increasing and between 32 mph and 65 mph - normal mode.
^ Speed increasing and above 65 mph - sport mode.
^ Speed decreasing and above 61 mph - sport mode.
^ Speed decreasing and between 61 and 28 mph - normal mode.
^ Speed decreasing and between 28 and 2 mph - comfort mode.
^ Speed decreasing and below 2 mph - sport mode.

Lateral Acceleration Input
The lateral acceleration switch is used for lift, dive and roll control. The sport mode is selected if the switch is activated by lift, dive or roll conditions. The system returns to its speed dependent mode 2 seconds after the switch returns to the inactive state.

Fault indicator
Any system error causes the fault indicator to illuminate. The fault indicator remains lit as long as the diagnostic trouble code is active. If the fault corrects itself, the fault indicator turns off, but the diagnostic trouble code is retained in the CCR controller's memory. Diagnostic trouble codes are stored In the CCR controller's non-volatile (EEPROM) memory.

If a diagnostic trouble code is set, a 1 second self-diagnostic test is performed at 3 minute intervals. The fault indicator comes on during this test and goes out if the fault is corrected. if the fault still exists, the indicator remains on.