Exhaust cam actuator

what is exhaust cam actuator? when should it be replaced?

Never heard of such a part. Sounds like a muffler belt or turn signal fluid to me.

If you have a DOHC engine, it could be the exhaust valve camshaft which normally does not need replacing, ever.

It does seem to exist. I was curious, beyond that I have no more info.

It’s hydraulically actuated by the engine oil so the condition of the oil affects it. If you’re using the factory oil life monitor to schedule oil changes (or you’ve been running an extended change interval of your own) and the ECA error code just popped up, try changing the oil first.