1995 E320 humming throttle actuator

[kidMoBile]

While retrieving codes last week, I noticed a significant amount of noise coming from the throttle actuator (directly under the plastic air intake) when the ignition was turned to the on position but the car was not running. It's a high-pitched squeal that changes pitch slightly when the gas pedal is depressed. The noise is constant....it also changed pitch when the codes I retrieved were being erased. I don't recall hearing this before. Is this normal or indicative of a faulty actuator or one that is on it's way out?

Thanks. Brian