A Monroe® example
Tenneco, parent company of the Monroe brand, currently offers car manufacturers a range of electronic damper technologies under its Monroe Intelligent Suspension name. One of these technologies — Continuously Variable Semi-Active Suspension (CVSA) system — is already well established within the North American vehicle population as an option on some German-branded vehicles and might begin to appear in your shop.
Developed by Tenneco in conjunction with Öhlins Racing, the CVSA system is a semi-active suspension that continuously adjusts damping levels according to road conditions and vehicle dynamics, such as speed, turning and cornering, delivering comfort without sacrificing the safety of sure handling.
A powerful Electronic Control Unit (ECU) triggers the CVSA system. Found at the heart of the CVSA unit, the ECU is designed to exploit the full potential of the electro-hydraulic valving system by processing input data sent by a group of sensors placed at key locations on the vehicle. Additional input signals are provided from other modules sharing the CAN (Controller Area Network) bus. The CVSA utilizes control software that processes the sensor information regarding steering wheel angle, vehicle speed, brake pressure and other chassis control information and sends signals that independently adjust the damping level of each shock absorber valve. CVSA dampers allow a large separation between maximum and minimum damping levels and adjust instantaneously to ensure the optimum in ride comfort and firm, safe vehicle control.
The first generation of CVSA went into production in 2003 as standard equipment on the Volvo R-line and as an option on the S80, V70, and S60. CVSA shocks also have been offered on several models manufactured by Audi, BMW, Mercedes-Benz, Volvo, and Volkswagen. Ford has also used CVSA technology on its S-Max, Galaxy and Mondeo.
Service and diagnosis
According to Joe Bacarella, manager, product training and Technical Resource Centers for Tenneco, the company’s electronic dampers are robust and suffer few premature failures. “In the unlikely event that they should fail, this would most likely be due to age and mileage,” he says.
Some of the service and inspection procedures you know so well from dealing with conventional dampers apply to these electronically controlled units. The traditional “bounce” test can be used to check for noise concerns, binding damper assemblies and even to monitor for a change in switch states on some makes. Active fluid leakage might also be a cause for replacing the damper assembly.
The troubleshooting mistakes that many are making, though, center on the testing of the electronics. And it starts with a check for related Diagnostic Trouble Codes. The DTCs related to the ride control system are not recorded in the Engine Control Module. These codes are logged in a dedicated control module or the Body Control Module, requiring a scan tool capable of accessing these ECUs. Relying on the data provided by a generic tool is causing many techs to miss needed information.
“Techs need to be aware that replacing these units will ‘turn out the light’ when the code specifically indicates an issue with a damper, or a solenoid that is integrated into the damper,” Bacarella cautions. “Many techs are not as aware of diagnosing BCM issues as they are with ECMs. They’ve been taught how to read and resolve engine-related DTCs but unfortunately some of these classes don’t explain that there are other codes to be found.”
And making the same mistake is easy to avoid. Most professional grade scan tools offer enhanced scan modes for families of manufacturers - domestic, Asian and European. Tools made in the last decade or so with enhanced capabilities also allow the user to perform an “all system scan,” a poll of all accessible modules on the network, and provide a list of any diagnostic codes stored and the module that logged them. This is a good practice to follow any time you connect to the vehicle’s Diagnostic Link Connector.
Apply a solid process
Once you have the code(s) retrieved, avoid another common troubleshooting mistake — assuming the cause of the code simply by its description. “(Some) often confuse a diagnostic code for a leveling issue with a damping issue,” observes Bacarella. “As an example, Volvo Suspension Module codes SUM-E000 through SUM-0337 are all related to the electronic suspension. However, the majority of these codes are related to issues with the sensors.” And replacing an expensive electronic damper isn’t going to turn the light off for those codes!
When dealing with any electronic system, it is a best practice to first retrieve all related DTCs. The next step is to take the time to read up on the individual code’s enabling criteria and the conditions required for the code to be recorded by the governing ECU. This may also require some reading up on the system’s theory of operation if you’re new to working on these intelligent suspensions. Once you have a basic understanding of how the integrated sensors and components function together, you can begin laying out your test procedures to isolate the cause of the code(s).
Be sure to check for any related Technical Service Bulletins. These are, after all, electronic systems controlled by a computer, and sometimes all that is needed to correct the DTCs and restore proper operation is a reprogramming of the controlling ECU or a recalibration of an input sensor.
Of course, if you are really new to electronic suspension work, seek out training. Tenneco’s Bacarella leads the effort related to Monroe products. Options range from live classroom sessions to technical forums. To begin your quest for knowledge, start with the “Resource Center” link at www.monroe.com or visit the “TennecoInc” YouTube channel.
Install and options
Removal and installation of electronic suspension dampers is relatively straightforward and similar to replacing a conventional unit. Check the model-specific procedure in your service information system, as some components (input sensors, for example) may require an initialization or relearn procedure.
What about those customers who have older cars but can’t afford to replace these often expensive units when needed? Tenneco offers Monroe kits designed to replace these units with conventional assemblies.
Bacarella offers some advice to consider before recommending this option: “Most of these kits are designed to replace the dampers when they are hydraulically or electronically bad. However, they are not designed to correct an issue with a bad sensor or air compressor. Some technicians tend to install these kits whenever there are any codes related to the electronic suspension system. Since many of the electronic suspension sensors are integrated into other systems, they require that the electronic control system remain functional. Consequently, installation of the kit does not always take care of any suspension-related DTC.”
Bacarella adds, “Since the cost of replacing electronic dampers on an older vehicle is sometimes cost prohibitive, we offer non-electronic options in conversion kit form for many applications. These kits often include the necessary components or instructions required to keep the electronic damper warning lights off; in rare cases, bypassing the ECU monitors is not an option.”
The electronic ride control service market is yet another potential revenue source for your shop, but as is the case with any relatively new technology, success is dependent on education and proper tooling. Perform a proper diagnosis, install a quality product, and add to your bottom line!
Call the Tenneco Technical Resource Center for the product support you need to get the job done. Available Monday through Friday from 8:30 a.m. to 5:30 p.m. EST, the company’s ASE-certified representatives are available to answer your product questions and provide technical assistance.