To "reset" the ECU, all you have to do is remove the source of backup power. To keep the memory alive while the car is off, the ECU has a direct line, through a fuse, that goes right to the battery. This is usually the same line and fuse that supplies backup power to your radio so it doesn't forget all of its settings.

Does removing battery reset ECU?

A. It depends on the car's age and type of ECU used. On some older cars, disconnecting the battery will reset the system but in most new cars it does nothing, except potentially reset the clock and radio station presets. ... Some ECUs have "adaptive learn" features for auto transmissions.

How do I reset my ECU without a scanner?

After removing the battery cables, you should proceed to cycle the ignition switch to the ON and OFF position for 3 to 5 times. Press on the horn button in the steering wheel. Keep it pressed for 30 seconds to a full minute to drain out all the stored power in the ECU capacitor. The horn is connected to a hot circuit.