Check air suspension light is on and the rear is low

A technician or mechanic can check this, but the most common problems are:
1) An electrical failure of some part, for example the switch or the relay that activates the compressor, or
2) the compressor itself could have failed.
God bless your efforts.

Would need to know what DTC'S - diagnostic trouble codes are stored in the module for the autoride suspension . Hooking up a professional type scan tool ,looking at input data to the module etc... Looking at a wiring diagram an testing electrical circuit's using a DMM - digital multi-meter . Reading how the system works ,what all involved in making the system work . This is how a professional Tech would go about diagnosing this .

The automatic level control (ALC) system maintains a desired rear suspension position under all types of towing, hauling and loading conditions. The following components are involved in the operation of the ALC system:
• Air line tubing--Pressurized air from the ALC compressor is pumped to each of the rear shocks via air line tubing.
• Air drier--Pressurized air from the compressor is run through a drier containing a moisture absorbing chemical preventing water accumulation in the rear shocks.
• Compressor--Supplies pressurized air to the rear shocks
• Compressor motor relay--The relay supplies battery positive voltage to the ALC compressor motor.
• Pressure sensor--The electronic suspension control module (ESCM) module provides a 5-volt reference and low reference to the ALC pressure sensor. The module receives the signal voltage that is relative to the air pressure applied to the rear shocks.
• ESCM--Controls the ALC system and electronic suspension control (ESC) system and detects failures in both. The module monitors inputs from the position sensors, and pressure sensor to determine when to raise and lower the vehicle to trim height as the vehicle is loaded or unloaded. The module limits pump activation to 255 seconds to prevent thermal damage.
• Exhaust valve--An electric solenoid activated by the ESCM to vent air pressure from the rear shocks.
• Left and right rear suspension position sensors--The 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 rear suspension ride height
• Left and right rear shock absorbers with internal air chambers and dampers--Dampens the rear suspension and maintains trim height depending on the air pressure applied.

Having it hooked up to a factory scan tool would be your best bet . Check for DTC'S diagnostic trouble codes . Without testing ,code scan ,we'd only be guessing .
Very complex , the untrained person hasn't got a pray of fixing this . You have no idea what your dealing with . Vehicle Dynamic Suspension The vehicle dynamic suspension consists of the following components:

• Rear air suspension control (RAS) module (5A919)
• Snorkel
• Drier
• Air compressor (5319)
• Air suspension switch (5K761)
• Solenoid valve (5311)
• Air spring (5560)
• Air suspension height sensor (5359)
• Air line
• Rear Air Suspension Control Module
  A microprocessor controls the air suspension system. The microprocessor and its supporting hardware are contained in the rear air suspension control module. The rear air suspension control module responds to signals from various sensors in the vehicle to maintain the programmed ride height while the vehicle is either moving or stopped. The rear air suspension control module accomplishes this by opening and closing solenoid valves to control the amount of air in the air spring(s). The rear air suspension control module turns on the compressor by applying voltage through the compressor relay to inflate the air spring(s) and raise the vehicle. The rear air suspension control module opens the vent solenoid to lower the vehicle by releasing air from the air spring(s) in response to signal inputs from the air suspension height sensor(s).
• Rear Air Suspension Control Module Diagnostic Trouble Code (DTC) Index DTC Description Source Action B1317 Battery Voltage High Rear Air Suspension Control Module GO to Pinpoint Test C . B1318 Battery Voltage Low Rear Air Suspension Control Module GO to Pinpoint Test C . B1342 ECU Is Defective Rear Air Suspension Control Module INSTALL a new rear air suspension control module. REFER to Module-Air Suspension Control . TEST the system for normal operation. C1441 Steering Sensor Channel A Circuit Failure Rear Air Suspension Control Module REFER to Section 211-00 . C1442 Steering Sensor Channel B Circuit Failure Rear Air Suspension Control Module REFER to Section 211-00 . C1722 Air Suspension Height Sensor Power Circuit Short to Power Rear Air Suspension Control Module GO to Pinpoint Test D . C1723 Air Suspension Height Sensor Power Circuit Short to Ground Rear Air Suspension Control Module GO to Pinpoint Test E . C1760 Air Suspension Rear Height Sensor High Signal Circuit Failure Rear Air Suspension Control Module GO to Pinpoint Test F . C1763 Air Suspension Rear Height Sensor High Signal Circuit Short to Ground Rear Air Suspension Control Module GO to Pinpoint Test G . C1765 Air Suspension Rear Height Sensor Low Signal Circuit Failure Rear Air Suspension Control Module GO to Pinpoint Test F . C1768 Air Suspension Rear Height Sensor Low Signal Circuit Short to Ground Rear Air Suspension Control Module GO to Pinpoint Test H . C1770 Air Suspension Vent Solenoid Output Circuit Failure Rear Air Suspension Control Module GO to Pinpoint Test I . C1773 Air Suspension Vent Solenoid Output Circuit Short to Ground Rear Air Suspension Control Module GO to Pinpoint Test J . C1790 Air Suspension LR Air Spring Solenoid Output Circuit Failure Rear Air Suspension Control Module GO to Pinpoint Test K . C1793 Air Suspension LR Air Spring Solenoid Output Circuit Short to Ground Rear Air Suspension Control Module GO to Pinpoint Test L . C1795 Air Suspension RR Air Spring Solenoid Output Circuit Failure Rear Air Suspension Control Module GO to Pinpoint Test M . C1798 Air Suspension RR Air Spring Solenoid Output Circuit Short to Ground Rear Air Suspension Control Module GO to Pinpoint Test N . C1813 Air Suspension Vent Request Exceeded Max Timing Rear Air Suspension Control Module GO to Pinpoint Test O . C1818 Air Suspension Air Compressor Request Exceeded Max Timing Rear Air Suspension Control Module GO to Pinpoint Test P . C1830 Air Compressor Relay Circuit Failure Rear Air Suspension Control Module GO to Pinpoint Test Q . C1832 Air Compressor Relay Circuit Short to Power Rear Air Suspension Control Module GO to Pinpoint Test R . C1840 Air Suspension Switch Circuit Failure Rear Air Suspension Control Module GO to Pinpoint Test S . C1842 Air Suspension Switch Circuit Short to Power Rear Air Suspension Control Module GO to Pinpoint Test D . C1897 Steering VAPS Circuit Loop Failure Rear Air Suspension Control Module REFER to Section 211-00 . U1041 SPC Invalid or Missing Data for Vehicle Speed

Check the air lines for leaks especially around the right rear tire area. chances are the flat tire severed or pulled loose one of the lines from compressor

There has been a service bulletin for that type of concern. Here is what it states.









Suspension - Rear Suspension Is Low/Sagging/Uneven

Notes




ENGINEERING INFORMATION

Bulletin No.: 06-03-09-006B

Date: December 15, 2008
Subject:
EI06006 - Rear Suspension Uneven, Sagging, Low (Recalibrate Air Spring Sensor)

Models:
2006-2007 Buick Rainier
2006-2007 Chevrolet TrailBlazer SS
2006-2007 GMC Envoy, Envoy XL
2006-2007 Saab 9-7X


with Suspension Pkg - Rear Load Leveling (RPO G67)

Supercede:

This bulletin is being revised to update the labor operation in the warranty information. Please discard Corporate Bulletin Number 06-03-09-006A (Section 03 - Suspension).

Condition

Some customers may comment on the rear suspension being uneven or sagging.

Correction

DO NOT REPLACE THE COMPRESSOR.

Based on technician feedback, engineering has determined that the customer's concern can be corrected by recalibrating the air spring sensor. Refer to the Trim Height Uneven or Low diagnostics and Air Spring Sensor Calibration procedure found in SI.

I believe this light comes on when there is one of several issues. Some symptoms are: Ball Joints worn, tie rod ends, vibration, bad tire(low Pressure also), alignment, pulling to left/right, shocks F/R check some of these and you may locate why light came on. Wayne

It is your air ride suspension. It could be the air bags, the sensors, compressor, wires and many other things. What I did was bought an after market coil spring suspension and converted it from the air ride suspension. The air ride is lovely but costly. It is hard to diagnose that air ride suspension without spending a lot more money then you want. I suggest getting an after market converter kit, but I would make sure it has the sensor plug so that your warning light on your dash goes out....otherwise it will be on forever!

There is an air compressor mountedmabove the rear suspension. The fuse for the air ride suspension is located behind the trunk rear trim panel. There is a level sensor on the rear control arm. If fuse is good, check for power at plug feeding compressor, compressor failure common. With suspesion at low position, sensor should send power to compressor. if no power suspect height sensor. Check relay for power and operation although failure rare.

you have to have air suspension computer scaned to pull codes in order to find problem,if rear is all the way up, it could be a bad rear level sensor it may be no good or the arm from sensor to car frame may have fallen off, hope this helps.

rear suspension ride leveler mslfunction. Check Air compressor function.