DESCRIPTION
Note. Electronic suspension system may also be referred to as the Load Levelling Control system, Dynamic Suspension system or Automatic Ride Control (ARC) system.
On 1998 models, air suspension system includes front and rear air adjusted system. On 1999 models, only rear suspension is air adjusted. Front and rear air adjusted suspension is air-operated and computer-controlled. Optional air suspension system utilizes air adjustable shock absorbers to provide variable vehicle ride height depending on load and driving conditions. Shock absorbers also incorporate computer controlled two-stage (firm and soft), damping capability. Smooth ride is provided for normal driving conditions. If conditions require additional shock absorber damping, air suspension control module adjusts each shock absorber separately in response to load, road and driving condition inputs received from 2 suspension mounted height sensors, Vehicle Speed Sensor (VSS), Throttle Position Sensor (TPS) and 2 steering sensors. On 4WD applications, transfer case inputs are also utilized.
OPERATION
Air suspension system is operational with ignition switch in RUN position, and has limited operation for 40 minutes after ignition is turned off. The air suspension switch, located in left rear corner of vehicle, must be turned off when vehicle is being hoisted, towed or jump-started.
A CHECK AIR SUSPENSION warning light is located in message center, to right of instrument cluster. Warning light stays on when air suspension is turned off or a system malfunction is detected.
Air required for leveling vehicle is distributed from air compressor to front (if equipped) and rear fill solenoids through nylon air lines. Air system can be pneumatically separated from side to side by control module activation of rear gate solenoid. This separation provides vehicle stability during roll conditions.
For safety during loading and unloading, vehicle height is memorized and maintained when any door is opened. Vehicle will return to commanded height when doors are closed or vehicle speed exceeds 10 MPH.
TEST A: MESSAGE CENTER INDICATES CHECK AIR RIDE SYSTEM (AFTER 20 MINUTES OF VEHICLE OPERATION)
- Connect New Generation Star (NGS) tester to Data Link Connector. DLC is located under steering column. Using manufacturer's instructions, check air suspension system. If air suspension control module is communicating, go to next step. If ARC module is not communicating, go to «TEST C»(ref-1320-S25462336982000031300000) .
- Perform on-demand self-test. Retrieve any stored DTCs. . If no DTCs are stored, go to next step. If DTC(s) are stored, go to appropriate test. See «ELECTRONIC AIR SUSPENSION SYSTEM DTC INDEX»(ref-1320-S03339665192000031300000) under DIAGNOSIS & TESTING.
- Using NGS tester, monitor PID VBATARC. If greater than 11 volts is indicated, go to next step. If 11 volts or less is indicated, charge or replace battery as necessary. Retest system for normal operation.
- Using NGS tester, trigger active command MC NORMAL ON and then MC NORMAL OFF. If CHECK AIR RIDE SYSTEM message disappears and reappears, go to next step. If CHECK AIR RIDE SYSTEM message does not display as described, repair Dark Green/Light Green wire as necessary.
- Monitor PID RUN. If IGN_RUN is not set to HIGH, replace power distribution box fuse No. 10 (15-amp) and/or repair Gray/Yellow wire as necessary. If IGN_RUN is set to HIGH, check message center. If message center is okay, replace control module. See «AIR SUSPENSION CONTROL MODULE»(ref-1320-S02562899432000031300000) under REMOVAL & INSTALLATION. Perform «RIDE HEIGHT»(ref-1320-S11017440782000031300000) procedure under ADJUSTMENTS. After repair, repeat air suspension control module diagnostics.