Motor relay
From Transformers Wiki
Motor relays were a component of Transformer anatomy which allowed them to move about and use their limbs. Severing it meant that the Transformer was left in a state of suspended animation.
Fiction
The Transformers cartoon
After Optimus Prime fell into a trap laid by Megatron, the Decepticon leader severed his motor relays leaving the Autobot powerless and immobile. City of Steel
