Quote:
Originally Posted by The Radium King
apologies, i was using the terms interchangeably. they are typically both replaced when servicing the engine, show the same symptoms when fail, and are sold together as a unit by porsche - 99610505158.
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No worries, I just wanted to point out that these are different parts so the OP won't get confused. You can replace only the solenoid when it fails, it's easy to test, replace and relatively cheap. Especially compared to the whole actuator unit, which is pretty pricey. The actuator is actually rebuildable, you can get it rebuilt using new O-rings so you won't have to buy the whole entire unit for $$$.
When the solenoid fails the resistance in its coil will go infinite which the DME will see and throw a code. If the O-rings fail the changeover will be sluggish because the piston in the actuator won't hold oil pressure, this triggers a different code. When it fails completely that's when the green rubber debris is all over the sump.
Apart from these two, the most typical failure is the worn chain pads that also causes similar problems and codes because it will affect changover and timing. This is the most dangerous also, because if the chain pad disintegrates completely the small chain will run on bare metal letting steel debris get in the engine and the chain eventually jumps over causing valve to piston contact and subsequent catastrophic failure.