How to Reset the ECU on Vehicles

by Contributing Writer; Updated June 12, 2017

You can reset the Electronic Control Unit (ECU) Vehicles the Vehicles right from your home garage. No special tools are needed to do the job and it will only take a few minutes of your time. The Vehicles comes equipped with an On-Board Diagnostics computer that monitors all functions of the Vehicles. The "Check Engine" light illuminates on the instrument panel when there is a problem with the ECU. After any necessary repair work is done, you can turn off the light and reset the ECU in a few short steps.

Under The Hood:

 How to Reset the ECU on a Ford Contour

Place the Contour's transmission in park (automatic transmission) or first gear (manual transmission). Engage the emergency brake and turn the ignition to the "Off" position. Rotate the ignition back to the "On" position but do not start the engine.

Plug the scan tool's data cable into the Contour's diagnostic data port, underneath the dashboard just above the pedal area. Turn on the scan tool and allow it to start up.

Follow the instructions on the scan tool's screen to enter engine and transmission information.

Choose "ECU" from the main menu. Select "Codes" and "Clear all current and stored DTCs." Wait for the scan tool to indicate that the codes have been cleared.

Unplug the tool's data cable from the diagnostic data port. Start the engine and ensure that the service engine light is not illuminated.

Items you will need

  • Automotive scan tool

 How to Reset an ECU on a 2004 Nissan Maxima

Shift the Maxima's transmission into park (automatic) or first gear (manual). Shut off the engine and set the parking brake. Turn the ignition back to the "ON" position but don't start the engine again.

Find the Maxima's diagnostic data port. It is located underneath the dashboard on the driver's side, just above the pedals.

Plug the scan tool's data cable into the Maxima's diagnostic data port and power on the scan tool. Wait for the scan tool to boot up.

Select "ECU" from the tool's main menu, then choose "Codes." Select "Clear all current and stored DTCs." DTC is an acronym for "diagnostic trouble code."

Allow the scan tool to clear the codes from the ECU's memory. Disconnect the scan tool from the diagnostic data port once the display indicates that the codes have been cleared. Start the engine and verify that the SES light is not illuminated. The ECU has been reset.

Items you will need

  • Automotive scan tool

 How to Reset the ECU for the 300ZX

Put the key in the ignition and turn it to the "On" position, but don't start the engine.

Press down on the accelerator very fast five times within five seconds. You have to press the pedal all the way to the floor each time. Wait 10 seconds.

Press the accelerator to the floor and hold it for 10 seconds, or until the "Check Engine" light turns on and off. Repeat this step again.

Turn off the ignition and wait about three minutes. Start the engine and examine the instrument panel. The Check Engine light should now be off and the ECU reset.

 How to Reset the ECU on a Nissan Serena

ECU Clearing Through Battery Disconnect

Disconnect the negative (black) cable from the car battery terminal, place to the side and ensure it does not touch the vehicle.

Disconnect the positive (red) cable from the car battery terminal, place to the side and ensure it does not touch the vehicle.

Pump the breaks or press the horn several times to drain the remaining power from the vehicle's electrical system. This allows for the capacitors (which store energy) in the ECU to fully deplete.

Leave the cables disconnected for an additional 5 minutes to ensure full depletion of energy from the ECU capacitors, then reconnect the battery cables. The vehicle's ECU will now be reset.

ECU Reset Through ECU Access

Locate the ECU under the driver's side dash of the Nissan. Remove the two nuts (usually 10mm) holding the device in place to fully access the ECU.

Place the starting key into the ignition and turn the key until the electronics mode is engaged. Do not start the vehicle.

Find the screw dial on the ECU. This dial is used to access the stored engine codes. Place a flat-head screwdriver into the dial and note the position of the screwdriver (not yet turned). The position noted is the original position and will be used to return the ECU to its normal state after clearing the codes.

Turn the dial clockwise until the dial stops turning. Pause one second and turn the dial counterclockwise until the dial stops turning--any error codes present will now be flashing on the dash through a series of blinking/flashing lights.

Turn the dial clockwise until the dial stops turning and wait for the flashing to stop. Once the flashing has stopped, pause one second and return the ECU to its normal state by turning the dial to the original position. The Nissan Serena's ECU should now be cleared. Remove the key from the ignition and return the ECU module to the original position. Install the retaining screws.

Items you will need

  • Flat-head screwdriver

  • Crescent wrench