Electropulse

An electropulse is an aspect of Transformer physiology and, if fading, meant they were slowly dying.

Fiction

The Transformers cartoon

When Optimus Prime was heavily damaged after a Decepticon attack, his electropulse was fading rapidly and would have meant his termination had he not been repaired. Divide and Conquer

Marvel The Transformers comics

Don't worry, I'll be back soon... about four issues later.

There is a device showing Powermaster Optimus Prime's electropulse on his destroyed torso. Still Life!