Diagnosing Air Ride Systems

Diagnosing Air Ride Systems

Air ride diagnostics is more than a spray bottle of soapy water. On today's late-model vehicles, it requires a scan tool, meter and scope. Swapping components will only lead you down a diagnostic black hole that leads to an angry customer and parts supplier. Modern air ride systems have a compressor and a module to control the flow of air to the struts or shocks. Control modules can have as many as 10 valves. They can also have three or more sensors to measure the pressure.

Air ride diagnostics is more than a spray bottle of soapy water. On today’s late-model vehicles, it requires a scan tool, meter and scope. Swapping components will only lead you down a diagnostic black hole that leads to an angry customer and parts supplier. 
Ride Height Sensors
In the past decade, the ride height sensor has changed dramatically. In the past, it was nothing more than a switch that engaged a relay to turn on the compressor so the vehicle would rise to the correct height. 
The next step in the evolution was a potentiometer that would change the voltage to tell the air ride control module the position of the suspension. 
 

The most sophisticated systems use a Hall effect sensor. This sensor can be used to show the position of the suspension with more precision. The sensors typically use two sensors in one unit for redundancy. The wave pattern will overlap much like a steering position sensor. 
Valves and Compressors
Modern air ride systems have a compressor and a module to control the flow of air to the struts or shocks. Control modules can have as many as 10 valves. They can also have three or more sensors to measure the pressure.
 
Purge and other valves can have sensors that measure the position. These sensor measure the position of the valves to detect problems that could cause an over or under inflation condition.  
Diagnostics
For any type Hall or resistance-type of ride height sensor to work, it requires the correct voltage and a good ground. If the ground is shorted or open it will produce a faulty reading or no information at all.
 
Testing these sensors can be done with a meter, scope or scan tool. With a meter, it is possible to observe changes in the voltage or resistance on both resistance and Hall effect sensors. It can also be used to measure voltage drop and the health of the grounds. 
 
Using a scope can yield more accurate information. A scope can be used to graph the voltage, resistance and even the wave pattern of a sensor as it is actuated. 
 
Scan tools are essential for working on some systems. Some enhanced scan tools can observe PIDs for the air ride system like valve operation, modes and vehicle position. Some new vehicles, like GM, have a calibration process for the ride control system.  
Information
Another key diagnostic tool is service information. Information on how the system behaves is critical in testing and diagnosing the system.
 
Information like pin-out valves, thermal protection and serial data bus communications can help you diagnosis the system right the first time. 
 
Some customers may complain of intermittent stiff ride or bottoming out after they get off the freeway. Or, they could complain that the vehicle does not handle well at high speeds. Without the service information, you could be behind the wheel a long time trying to repeat the customer’s complaint. 
 
With service information, you would realize that the system could have a highway mode that lowers the suspension for handling and fuel efficiency. Some air ride systems even drop the nose. 
The Reality
With the complexity of some air ride systems, repair of the system may not be economically viable. Some companies are offering conversion kits which switch the vehicle to a conventional system with hydraulic units and springs.

You May Also Like

Volvo Modular Engine Service

The Volvo Modular Series engine outlasted Ford and was retired by Geely. The Volvo modular design that can have four, five or six cylinders made its debut in 1990 in the 960 sedan as a six-cylinder and never stopped improving. VOLVO SPA AND CMT What is a Volvo? In 1999 the company was acquired by

The Volvo Modular Series engine outlasted Ford and was retired by Geely. The Volvo modular design that can have four, five or six cylinders made its debut in 1990 in the 960 sedan as a six-cylinder and never stopped improving.

VOLVO SPA AND CMT

What is a Volvo? In 1999 the company was acquired by Ford. By 2006 all of the boxy Volvo platforms were gone and replaced by Ford platforms. But, the engines remained uniquely Volvo. In 2010, Volvo was purchased by the Chinese automaker Geely, and the purge started again.

Audi Active Suspension Service

The key to servicing these systems is proper information and understanding precisely how these systems operate.

How To Service BMW Tire Monitor Systems

BMW has offered Tire Pressure Monitoring Systems (TPMS) for more than 20 years. These early indirect and direct systems were implemented not to meet the 2007 government mandate but to inform the driver when an expensive Michelin or Bridgestone run-flat tire was deflating. Some 2002 and 2003 models have an indirect system called Flat Tire

VW DSG Maintenance

A DSG transmission is lighter than a comparable automatic with the same number of speeds.

Tech Tip: Checking Transmission Fluid Levels When Cold or Hot

Checking the fluid level before the transmission has reached the specified temperature might cause a false reading

Other Posts

Servicing Mercedes-Benz AMG Brakes

Take a look at some of the things you need to know in order to service the brakes on a Mercedes-Benz AMG vehicle.

Air Ride Diagnostics: Reservoirs and Compressors

The secret to diagnosing air ride problems is knowing what criteria the system uses to regulate the compressor/reservoir and having the right tool.

Mercedes EQS Service Opportunities

EQ is the EV brand for Mercedes. It is the equivalent of Audi’s Etron.

BMW 4-Series Service

The 4-series does not stray far from the typical BMW engineering and operation.