Contents: Description ↧ ALC and ESC control unit ↧ Self-diagnosis system and error codes ↧ Shock absorbers ↧
GMT800. Suspension details: (2500 series, right rear). 1 - bridge beam, 2 - body height sensor, 3 - sensor lever, 4 - body height sensor connector.
GMT800. Suspension parts (1500 series, left rear). 1 - shock absorber, 2 - frame, 3 - shock absorber electromagnetic valve connector.
GMT800. Suspension parts (Suburban/Yukon XL). 1 - frame, 2 - sensor connector, 3 - body height sensor (left front).
GMT800. Suspension component connector locations. Front frame. 1 - shock absorber electromagnetic valve (left), 2 - wheel speed sensor (left), 3 - wheel speed sensor wires (left), 4 - body height sensor (left), 5 - body height sensor wires (left), 6 - chassis wire harness, 7 - shock absorber electromagnetic valve (right), 8 - wheel speed sensor (right), 9 - body height sensor (right), 10 - frame.
GMT800. Suspension parts (2500 series, left rear). 1 - shock absorber, 2 - shock absorber electromagnetic valve connector, 3 - frame.
GMT800. Location of suspension component connectors. Left rear of the passenger compartment (Escalade EXT). 1 - rear object sensor control unit, 2 - connector, 3 - automatic level control (ALC) and electronic shock absorber control (ESC) control unit, 4 - connectors, 5 - left rear seat bracket.
GMT800. Location of suspension component connectors. Right rear of the passenger compartment (except Avalanche/Escalade EXT). 1 - inner side panel of the body, 2 - body wire harness, 3 - connector C1 of the control unit, 4 - connector C2 of the control unit, 5 - connector C3 of the control unit.
GMT900. Control unit location. 1 - right rear suspension spring, 2 - body height control unit (ALC) and shock absorber stiffness control unit (ESC), 3 - frame.
GMT900. Suspension component connector locations. Rear of frame. 1 - body height sensor (left), 2 - body height sensor (right), 3 - frame, 4 - wheel speed sensor (right), 5 - shock absorber electromagnetic valve (right), 6 - body height control system compressor 7 - shock absorber electromagnetic valve (left), 8 - wheel speed sensor (left).
GMT900. Suspension component connector locations. Front frame. 1 - wheel speed sensor (right), 2 - shock absorber electromagnetic valve (right), 3 - body height sensor (right), 4 - body height sensor (left), 5 - shock absorber electromagnetic valve (left), 6 - wheel speed sensor (left), 7 - frame.
GMT900. Relay location. 1 - body height control system relay, 2 - mounting block in the engine compartment.
Description
The following systems can be installed on the vehicle. There are two systems: Automatic Level Control (ALC) and Electronic Suspension Control (ESC). ALC system (automatic body leveling system) maintains the height of the body at a given level depending on road conditions. This system regulates the height of the rear part of the body only. And the ESC system (shock absorber stiffness adjustment system), which changes the operating parameters of all 4 shock absorbers depending on road conditions.
Both systems operate in real time. The electronic suspension control unit (ESC) activates the electromagnetic valves of the suspension shock absorbers and processes signals from the height sensors of the body; on 1500 series vehicles, the electronic control of the stiffness of the shock absorbers (ESC) is part of the body leveling system (ALC).
ALC and ESC control unit
The job of the ESC unit is to provide a higher level of control over the vehicle (compared to the parameters of suspension with passive shock absorbers) in both off-road and on-road driving modes. The control unit monitors ride height, vehicle speed, steering wheel position and speed, shock absorber compression/rebound status and trailer switch status in real time and immediately selects "normal" or "hard" damping for each shock absorber to adapt the suspension to specific driving conditions.
The suspension control unit will also use the rear wheel position relative to the body and vehicle speed to maintain the ride height at the desired level. On 1500 Series models with ALC and ESC, the control unit will be active for approximately ten minutes after the ignition is switched off.
Self-diagnosis system and error codes
The control unit performs diagnostics of the system. After four consecutive ignition cycles, if a malfunction is present, the corresponding malfunction code is recorded in the unit's memory and a message appears on the information display "SERVICE RIDE CONTROL" (suspension maintenance).
The electronic control unit switches to emergency control mode and limits the speed to 80 mph (128 km/h).
The diagnostic trouble codes can be read using a diagnostic scanner. After diagnostics and further troubleshooting, the diagnostic trouble codes must be deleted from the control unit memory. For more information, see chapter "Error codes".
Body height sensors The control unit supplies a stabilized supply voltage of 5 volts to all four body height sensors and to the air pressure sensor and receives analog signals from the sensors in the range of 0.5-4.5 V.
Shock absorbers
The shock absorber has two electromagnetic valves built into the piston with a winding resistance of 1.5-3.3 Ohms. The response time of the shock absorber to the control signal is less than 40 milliseconds. To achieve the damping effect, the shock absorber uses the flow of working fluid through calibrated holes. The shock absorber valves are controlled by the ESC unit.