How to Perform a Throttle Relearn on Your Mercedes-Benz
If you’ve noticed that your Mercedes-Benz vehicle has reduced throttle response, hesitates during acceleration, or the RPMs are lower than normal, it may be time to perform a throttle relearn procedure. This simple process resets the electronic throttle actuator so that it relearns the proper closed throttle position. It allows the engine control unit (ECU) to adapt to your driving style again.<>
The throttle relearn procedure is also known as a throttle body alignment or accelerator pedal calibration. It applies to most modern Mercedes-Benz models that use an electronic throttle control system, also called drive-by-wire. This includes popular models like the C-Class, E-Class, S-Class, GLC, GLE, GLS, and many others.<>
Applicable Mercedes-Benz Models
The throttle relearn procedure can be performed on the following Mercedes-Benz models that use an electronic throttle actuator:<>
- C-Class (W203, W204, W205)
- E-Class (W211, W212, W213)
- S-Class (W220, W221, W222)
- CLS-Class (C219, C218, C257)
- SLK-Class (R171, R172)
- CLK-Class (W209)
- SL-Class (R230, R231, R232)
- GLK-Class (X204)
- M-Class/GLE-Class (W163, W164, W166)
- GL-Class/GLS-Class (X164, X166, X167)
- G-Class (W463)
- GLC-Class (X253, C253)
- GLA-Class (X156, H247)
- Sprinter (W906, W907)
If your Mercedes-Benz model is not listed above, consult your owner’s manual or a certified Mercedes-Benz technician to confirm if the throttle relearn procedure is applicable to your vehicle.<>
Benefits of Performing a Throttle Relearn
There are several benefits to performing a throttle relearn on your Mercedes-Benz:<>
- Improved throttle response: After the relearn, you will likely notice snappier and more linear throttle response, similar to when the vehicle was new. The ECU adapts to your current driving style.
- Smoother acceleration: The vehicle may accelerate more smoothly with less hesitation after the throttle relearn. It can help resolve rough idle or stuttering during acceleration.
- Optimized shift points: For models with automatic transmissions, the shift points may change after the relearn to optimize power delivery. The RPM at which the transmission shifts can increase, allowing the engine to rev higher before shifting.
- Resolved check engine light: In some cases, a check engine light related to the throttle system may be resolved by performing the relearn procedure. However, if the light persists, have the vehicle diagnosed for potential faults.
- Better fuel efficiency: With the throttle actuator and ECU properly calibrated, the engine can operate more efficiently, potentially improving fuel economy.
Safety Precautions
Before beginning the throttle relearn procedure, follow these important safety precautions:<>
- Perform the procedure outdoors or in a well-ventilated area, as you will be working with the ignition on.
- Ensure the vehicle is in park (P) for automatics or neutral with the parking brake engaged for manuals.
- Do not touch the accelerator pedal or start the engine during the relearn process unless instructed.
- If you are uncomfortable performing the procedure, have it done by a qualified Mercedes-Benz technician.
Latest Throttle Relearn Tutorial
Follow these step-by-step instructions to perform the throttle relearn procedure on your Mercedes-Benz:<>
- Get in the driver’s seat and close all doors. Make sure the hood is closed.
- Insert the key into the ignition and turn it to the “on” position (the second position before starting the engine). For push-button start models, press the start button once without depressing the brake pedal.
- With your foot off the brake, press the accelerator pedal all the way to the floor and hold it there for at least 10 seconds. You may hear the throttle actuator clicking, which is normal.
- While still holding the accelerator pedal down, turn the ignition key to the “off” position. For push-button start, press the button again to turn off the ignition. Do not remove the key.
- Release the accelerator pedal.
- Wait at least 2 minutes for the ECU to reset and relearn the throttle actuator position. During this time, do not press any pedals, start the engine, or open the doors.
- After 2 minutes, start the engine normally. The relearn procedure is complete.
- Test drive the vehicle to feel if the throttle response and acceleration have improved. The ECU will continue to adapt to your driving style over time.
If the throttle relearn procedure does not resolve your throttle-related issues, there may be an underlying problem that requires diagnosis by a professional technician. Issues like a faulty throttle position sensor, damaged wiring, or a malfunctioning accelerator pedal cannot be fixed by the relearn.<>
Throttle Relearn vs. ECU Reset
A throttle relearn is often confused with an ECU reset, but they are two different procedures. An ECU reset, which Mercedes-Benz refers to as “Rebooting the ME-SFI Control Unit”, clears all adaptations and learned values from the engine control unit. This includes things like idle speed, fuel mixture, and transmission shift points.<>
The throttle relearn only resets the learned values for the electronic throttle actuator, specifically the closed throttle position. It does not affect other ECU adaptations. In most cases, a simple throttle relearn is sufficient to restore proper throttle operation. An ECU reset is more extensive and is typically done after modifications like an engine tune or to troubleshoot certain issues.<>
To perform an ECU reset, the battery negative terminal is disconnected for at least 15 minutes. This allows the ECU capacitors to fully discharge so it loses all stored data. Upon reconnecting the battery, the ECU will revert to its base programming with no learned adaptations. The throttle relearn procedure should be done after an ECU reset.<>
How Often to Perform a Throttle Relearn
Mercedes-Benz does not specify a service interval for performing a throttle relearn in the maintenance schedule. Most owners only do it as needed when they notice throttle-related issues. However, some enthusiasts choose to perform the relearn periodically, such as every 5,000-10,000 miles or with every other oil change.<>
Doing a throttle relearn too frequently will not cause any harm, but it is generally unnecessary unless you modify your driving style or notice a problem. If the throttle response feels fine, there is no need to do the relearn. Over time, the ECU will continue to adapt to your driving habits regardless.<>
One instance where a throttle relearn is recommended is after disconnecting the battery or if the vehicle has not been driven for an extended period. The learned throttle values can be lost if power is interrupted to the ECU. For this reason, it’s a good idea to perform a relearn after replacing the battery or if the vehicle has been in storage.<>
Troubleshooting Throttle Relearn Issues
If the throttle relearn procedure does not complete successfully or you still have throttle issues afterwards, there are a few things you can try:<>
- Check for fault codes: Use a compatible OBD-II scanner to check for any diagnostic trouble codes (DTCs) related to the throttle system. Common codes include P0120, P0121, P0122, and P0123 which indicate a problem with the throttle position sensor or its circuit. If codes are present, they need to be addressed before the relearn will be successful.
- Inspect the accelerator pedal: Make sure the accelerator pedal moves smoothly and returns to the top position when released. If the pedal is sticking, binding, or not returning fully, it can cause issues with the relearn. Clean the pedal hinge with throttle body cleaner and lubricate with silicone spray if needed.
- Check the wiring: Visually inspect the wiring harness going to the electronic throttle actuator for any signs of damage, corrosion, or loose connections. Pay special attention to the connector at the throttle body. Repair any damaged wires and ensure the connector is fully seated.
- Perform an ECU reset: If the throttle relearn still does not work, you can try doing a full ECU reset by disconnecting the batterynegative terminal for 15 minutes. This will clear all adaptations and allow the throttle actuator to relearn from scratch. Just be aware that you may need to relearn other settings like the transmission shift points afterwards.
- Consult a professional: If you’ve tried all the above steps and still have throttle issues, it’s best to have the vehicle diagnosed by a qualified Mercedes-Benz technician. There may be an underlying problem with the electronic throttle actuator, pedal position sensor, or ECU that requires special tools and knowledge to repair.
Final Words from Boss Erwin
Performing a throttle relearn on your Mercedes-Benz is a simple procedure that can restore the responsiveness and performance of the electronic throttle system. It allows the ECU to relearn the closed throttle position and adapt to your driving style. The procedure is done by pressing the accelerator pedal with the ignition on but engine off, then waiting a few minutes for the relearn to complete.<>
Most modern Mercedes-Benz models, including the popular C-Class, E-Class, and SUVs like the GLE and GLS, can benefit from a periodic throttle relearn. It’s especially helpful if you notice a decrease in throttle response, hesitation, or rough running. In some cases, it can even resolve a check engine light related to the throttle system.<>