Mercedes-Benz E-Class and E-Class AMG: How to Reset ECU

In order for the ECU to unlearn your driving habits, it requires a reset. After reset, the ECU begins "teaching" the transmission based on your current driving habits. Learn how to complete the reset here.

By Richard Bowen - May 4, 2015

This article applies to the Mercedes-Benz E-Class and E-Class AMG (2002-2009).

The ECU (electronic control unit) adjusts the transmission for shifting smoothness and for maximizing fuel efficiency. If you drive aggressively, the ECU "learns" this driving style and adjusts the transmission accordingly. If you drive a little more passively, for example, primarily on the highway, the ECU directs the transmission to operate according to this driving style. Use this quick step-by-step guide to reset the ECU in your Mercedes-Benz E-Class or E-Class AMG.

Materials Needed

  • Ratchet
  • Socket

Step 1 – Turn the car to ON

Insert the key into the ignition and turn the key to the ON position. Do not start the vehicle.

Figure 1. Turn the key to the ON position only.

Step 2 – Depress the gas pedal

Put your foot on the gas pedal and press the pedal all the way to the floor. Hold the pedal in this position for five seconds.

Figure 2. Depress the gas pedal for five seconds.

Step 3 – Turn car off and release the gas pedal

Put the key in the OFF position. Take your foot off the gas pedal to release it.

Step 4 – Wait

Wait one to two minutes, and the ECU will reset automatically.

Pro Tip

Resetting the ECU is not the same as "reflashing." Reflashing is where the dealer uses a computer to input codes that hard-code information into the ECU to factory or custom specifications. Race car drivers use AEM EMS (advance engine management/engine management systems) to tune the engine. These devices are not for use on a vehicle that you intend to drive on a public street or highway.

Step 5 – Test drive

Test drive your car to determine if your engine and transmission give you the response you would like. For example, if before resetting the ECU your car's response was sluggish due to highway settings, you should now feel quicker startups and more power from the motor.

Figure 3. Go for a test drive.

Step 6 – Reset PCM

Another method to reset engine parameters for better performance is to reset the PCM (powertrain control module). This module monitors fuel and air consumption. Follow this procedure:

  1. With the ignition off, lift the hood to access the car battery.
  2. Remove the battery cover.
  3. Unfasten the negative lead using your ratchet and socket; wait 15 minutes while the PCM resets.
  4. Re-fasten the negative lead to the battery; re-install the battery cover.
  5. Re-set the car's clock, radio stations, etc., as needed.
Figure 4. Unfasten the negative (black) lead.

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