An electromagnetic pulse (or EMP) is a magic event which disables or destroys some electronic/robotic devices, but leaves others conveniently operational.
Super Robot Lifeform Transformer manga
Devil's Due G.I. Joe vs. the Transformers
Blackout wipes out the military base with EMP bursts.
Sector Seven ARG
Capture the Cube
Dewbot is not resistant to an electromagnetic pulse, but the guards are.
Revenge of the Fallen (film)
Starscream disables military communications in Egypt by setting off an EMP.
During his days in the Great Wars, Ratchet carried a small EMP generator on his arm. He used this device on low power settings to place patients under general anesthetic, allowing him to perform painful or complex operations without causing the patient discomfort. He described its operation to Arcee, telling her it would "temporarily overload your consciousness center." At higher settings, the device is capable of immediately rendering a Transformer unconscious, even at range, and can also erase memory cores. Unfortunately, the generator was stolen by Lockdown, who used it as a weapon for many years before Ratchet was able to recover it. When Lockdown tried using it on Ratchet, Ratchet revealed that he was immune to it because he's the device's creator.
In the present, on Earth, Ratchet and Bumblebee can create a directed EMP by "crossing the streams", so to speak, of their respective magnetic and electric weapons. Some combination of this EMP and the Key was seemingly responsible for granting sparks to the lifeless Dinobots.
The two later used the same kind of electromagnetic pulse to successfully blast Blitzwing out of the air.
Later, Ratchet was forced to use his EMP generator on an out of control Sari, despite the fact that he didn't know how it would affect her, since the latter is part Cybertronian and part human.