bobarry : ..... So, I'm guessing the error code is tripped by failure of whatever FUNCTION the solenoid is supposed to do, and not by a resistance reading or the position of the plunger.
Conclusion: Should I spend $36 times 2 and change them both?
The solenoid valves in question change their respective cam timing when they are actuated. Each has an associated sensor that provides feedback about the actual camshaft position. There are actually several possible failure modes, and any of them will result in the same fault code(s).
1) The wiring could be faulty.
2) The solenoid coil could fail, either open or shorted.
3) The solenoid valve spool could be stuck.
4) The oil flow to or from the valve could be blocked or inadequate.
5) The camshaft actuator could be stuck or broken.
6) The position sensor (or its wiring) would be faulty.
Yes. I would (and did) replace both solenoid valves.