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RENNtech's FAQs | Frequently Asked Questions 


RENNtech Performance Parts vs. Factory Warranty.

Crank vs. Wheel Horse Power

Why does the Manufacturer not program the OEM ECU as your unit is programmed?

Is the ECU upgrade really as simple as unplugging the stock ECU and plugging in the RENNtech tuned ECU?

Will the RENNtech ECU remove the top speed limiter?

What is the turn around time for ECU’s sent to you for tuning?

How do I send my vehicles ECU to RENNtech?

Will I be receiving my ECU back or do you send me a RENNtech ECU in exchange?

Will regular dealer service work reset my ECU back to the factory setting?

Will adding additional performance parts at a later date necessitate the ECU to be reprogrammed?


RENNtech V3 Digital Suspension Lowering Module General Troubleshooting


RENNtech Performance Parts vs. Factory Warranty.

In the age of computer controlled diagnostic equipment, emissions control devices and ever increasingly complicated vehicle electrical systems; modern vehicle performance tuning has become just as complicated.

Who do you trust? Where do you go for service? What will happen to my new car factory warranty once I install aftermarket parts? Ask these questions or search on the internet regarding this issue and you are sure to get a slew of conflicting answers and misinformation.

Answers to these questions certainly are not written in stone but there are certain things most consumers are unaware of which only helps to feed the frenzy and confusion regarding aftermarket parts and service.

One fact that many consumers are unaware of is a United States federal law enacted in 1975 which governs warranties on consumer products (including automobiles) called the Magnuson-Moss Warranty Act (P.L. 93-637). In very brief summary, the law protects consumers with warranties written in an easily understood language and ensures warrantors cannot require that only branded parts be used with the product in order to retain the warranty (e.g. aftermarket parts on a vehicle). Basically, a warranty claim cannot be denied on your vehicle simply because of aftermarket or performance parts.

This means that when you decide to install an exhaust or lowering kit on your car and the engine fails, they cannot deny a warranty claim based solely on the fact that the vehicle was not stock. While an after market exhaust may void the warranty on the factory exhaust, it won’t deny you coverage on other components on the vehicle.

While the law is designed to protect consumers it is not a guarantee that a manufacture cannot deny your warranty. A manufacturer can still deny a claim if they deem that the aftermarket component installed caused the problem. This is why selecting a reputable company with quality parts that you can trust to install and service your vehicle should also play an important factor in your tuning decision.

RENNtech has been at the forefront of the tuning market for more than 21 years and stands behind all our products with a rock solid warranty. In fact, RENNtech continues to be the tuning choice of Mercedes Benz Dealerships who not only install and service our products, but work with RENNtech directly should the need for warranty arise.

Our products are designed to work in complete harmony with factory equipment and our tuning software does not over ride or negates any safety features built into the ECU. This ensures you gain mind blowing performance without sacrificing daily driver comfort or reliability. Even after two decades, we continue to be the tuning choice for Mercedes enthusiasts and ensure the same high level of craftsmanship, knowledge and passion goes into every product we put our name on. RENNtech truly is performance without compromise.




Why does the Manufacturer not program the OEM ECU as your unit is programmed?

There are many reasons why the factory ECU is not programmed the same way in which we program our units. Manufactures tunes are predominantly geared to many different important factors with performance becoming a consideration only after a multitude of other requirements are met.

The factory tunes their ECU’s to meet a wide variety of day to day driving conditions where fuel economy, emissions and local government regulations all play a part in deciding how the engine will perform in your specific vehicle. Other factors also include 

  • Insurance regulations in certain countries such as Europe
  • High speed driving
  • Catalytic converter Protection
  • Fuel grade and quality available in select markets
  • Drivability in a wide array of conditions, altitudes and climates
  • Company marketing strategies
  • Positioning of a specific model against the competition
  • Positioning of a model within the companies own model line up


Many manufactures also design a power train to work on multiple vehicle platforms across their production line. For example, the Mercedes M157 engine ( In 63 non turbo AMG vehicles) is found in ALL 63 series such as the C class, S, CL, CLS,E,ML,R and so on. Each of these models may have the same engine, yet has been tuned based on the vehicles unique characteristics with performance being a factor only after the majority of these requirements have been fulfilled.

RENNtech ECU tunes certainly take into account all the things the factory compensates for, but brings performance to the forefront of the equation. Our proprietary ECU tunes have been developed and rigorously tested in house for maximum performance, compatibility and reliability ensuring you have maximum performance when you want it, but retain the comfort of a daily driver when you don’t need it.

Our remapping optimizes performance by modifying the ignition timing, throttle mapping, fuel curves and air/fuel ratios. We also modify boost mapping on turbo charged vehicles as well as increase the rev limiter and the top speed governor; all of which brings out the true potential hidden within you vehicle. Our modifications do not override any of the vehicles safety functions, nor does it interfere with any built in protection features from the factory so you can rest assured your performance tune will provide you with years of trouble free enjoyment.



Is the ECU upgrade really as simple as unplugging the stock ECU and plugging in the RENNtech tuned ECU? 

Yes! Our ECU upgrades are designed to be plug and play requiring little more than removal of the stock unit and replacement of the ECU when it is returned to you from RENNtech. The ECU connectors are easy to remove and install and their location cannot be confused. Each connector is unique and only fits on its designated counterpart. 

Our website support page (

features detailed instructions on the removal and replacement of the ECU for your specific vehicle. Live technical support is also available to support you should you have any additional question or require assistance during the process. Support is available M-F 9am- 6pm EST at (561)-845-7888



Will the RENNtech ECU remove the top speed limiter?

Our ECU program will increase the vehicles top speed to the MB recommended top speed based upon the tire rating for the vehicle. This is to ensure safe operating conditions and that the vehicle maximum speed does not go beyond that of performance DOT tire ratings.



What is the turn around time for ECU’s sent to you for tuning?

The typical turnaround time for an ECU upgrade is one (1) business day. ECU’s received during our morning shipment will be programmed and sent back out the same day.



How do I send my vehicles ECU to RENNtech?

Customers wishing to send their ECU into RENNtech for tuning can request ECU/TCU removal instructions from our sales team.

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Once the ECU is removed, please completely fill out and send the ECU information form with your ECU.  This form can be found here:

RENNtech ECU Order Form | Click Here

Ensure you provide adequate shipping insurance for package as RENNtech is not responsible for any lost packages or damage during shipping to or from our facilities.




Will I be receiving my ECU back or do you send me a RENNtech ECU in exchange?

Customers who purchase our ECU upgrade receive back the same ECU they sent into us for programming as the ECU is “married” to the vehicle. Program values, coding and adaptations are vehicle specific and would not allow for an exchange basis on ECU’s.




Will regular dealer service work reset my ECU back to the factory setting?

Newer vehicles can sometimes receive software updates from the dealer during a service. These upgrades to the ECU do overwrite the tuned file residing within the ECU. These dealer updates are generally a good thing can fix known issues or improve drivability. Customers who purchase an ECU upgrade and have the unit updated during a factory service will be eligible to have their vehicle reflashed by RENNtech or their authorized RENNtech dealer with a new tuning file based on the latest update currently installed in their vehicle. These updates are provided at no additional charge though the customer is responsible for shipping charges to and from our facilities.



Will adding additional performance parts at a later date necessitate the ECU to be reprogrammed?

This depends on the parts being added. Typically, simple bolt on components (such as an air box, mufflers, and post catalytic exhaust modifications) will not require an ECU to be reflashed. Dramatic changes to exhaust components pre catalytic (such as headers or higher flow sport catalytics) or the addition of boost on forced induction vehicles (55 series supercharged or biturbo engines) will require modifications to the ECU to accommodate for these upgrades and ensure maximum performance.




RENNtech V3 DLM General Troubleshooting

I’m changing settings in the DLM software, but nothing is happening

  • Make sure the drivers are installed.  When drivers are properly installed, the device serial number will show up at the top of the screen (SMxxxxx or VAGxxxxx).  If not, click on “Help” and “Install Drivers” to install. 

The front of the vehicle is lowering, but the back seems to be going up

  • On some vehicles, the polarity values of the sensors are reversed from the factory.  As a result these vehicles require a setting change in the DLM Software.  Under the “Settings” menu, click on “Channel Polarity” and change the option to “MB 215/164 Chassis”.

Vehicle shows “Airmatic Malfunction” or “ABC Malfunction” on the dash

  • This is typically an indication that a vehicle has been lowered too much.  First try to put DLM settings back to the RENNtech Recommended settings.  If problems persist, try bypass connector.  If bypass connector fixes problem, ensure correct wiring was followed.  After confirming wiring, contact RENNtech Support for assistance. 

Vehicle goes back to stock ride-height at around 30 mph

  • This is a normal function of the DLM.  To change the speed at which the suspension returns to factory height, open the DLM software and click on the “Speed Settings” tab.  To disable function, select a speed of 200mph.


Contact us

7825 SW Ellipse Way, Stuart, FL 34997
(+1) 561 - 845 7888
Mon - Fri 9am - 6pm


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7825 SW Ellipse Way - Stuart, FL 34997
TEL: 561.845.7888 FAX: 561.845.6777 E-MAIL: