Electronic Suspension Control Description and Operation

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The electronic suspension control (ESC) is the bi-state system providing optimal suspension damping as road and driving conditions change. The system also allows the driver to select a tow/haul mode to enhance the ride when trailering or with a loaded vehicle.

The following are involved in the operation of the ESC system:

Electronic suspension control module (ESCM)-Controls and detects failures in the ESC system. The ESCM controls the damping force at all 4 shock absorbers individually for a soft or firm ride. It receives inputs from vehicle speed, steering wheel position, suspension position, and lift/dive status to determine the amount of damper control to the shocks electrical solenoid.
Front/rear suspension position sensors-The ESC module provides a 5-volt reference and low reference to all 4 of the body-to-wheel suspension position sensors. The sensors send the ESCM a signal voltage that is relative to the suspension ride height used to determine the amount of damper control. The sensors valid range is 0.35-4.75 volts.
Front/rear shock absorbers with an internal electrical solenoid-The ESCM controls 0-100 percent of the pulse width modulated (PWM) current to the solenoid adjusting the fluid orifice size within the shock. This increases or decreases the suspension damping force in both compression and rebound directions.
Vehicle speed-The ESCM receives a serial data message for vehicle speed input, and is used to determine the amount of damper control.
Steering wheel position-The ESCM receives a serial data message for steering wheel position input and uses this as an indication of the position and rotation of the steering wheel to determine the amount of damper control.

The ESCM monitors the inputs from the front/rear suspension position sensors, vehicle speed, and steering wheel position. The ESCM calculates the inputs to control the amount of PWM current to the solenoid within each shock. This adjusts the fluid orifice size to vary the soft to firm damping force in both compression and rebound direction for the current road and driving conditions.

When the ESCM detects a malfunction and sets a DTC. The system disables, and defaults with a fail-soft action, then sends a serial data message for the driver information center (DIC) to display service suspension system and speed limited to 80 mph warning messages.

The ESC system uses an ignition cycling diagnostic approach in order to reduce the occurrence of false or intermittent DTCs that do not affect the functionality of the ESC system. This allows the fail-soft actions to be taken whenever a malfunction condition is current, but requires the malfunction to be current for 3 consecutive ignition on cycles before the corresponding malfunction code and message will be stored or displayed.