Electronic Suspension Control Description
The Electronic Suspension Control system is a Magneto-Rheological Real Time Damping (MRRTD) system and independently controls the fluid viscosity in each strut and shock absorbers to control the vehicle ride characteristics.
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 coil. |
| • | 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 struts/rear shock absorbers have an internal electrical coil, and micron sized metal particles in the fluid. |
| • | 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. |
| • | Suspension control switch--The suspension control switch has two positions,TOUR and SPORT. When the switch is placed in the SPORT position, a ground signal is received by the body control module (BCM). The BCM then sends a serial data message
to the ESCM to modify the shock damper rates which will change the ride and handling characteristics of the vehicle. |
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 0-100 percent of PWM current to the coil within each strut or shock, increasing
the fluids viscosity by aligning the metal particles with each other. This increases or decreases the suspension damping force in both compression and rebound directions.
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 Instrument Panel Cluster (IPC) to display SERVICE RIDE CONTROL and SPEED LIMITED 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.
