What year is the car? If time permits I can pull the pin point tests for you, with the VIN, I can run an Oasis report and see if there's any related TSB/SSM's attached to it. As pointed out above, that particular dtc is circuit related. While more and more, it's becoming critical to use the correct viscosity oil, in this case it should have nothing to do with the fault code set. Best short answer was pointed out in terms of disconnecting and reconnecting the solenoid valve, clear the dtc and see if it resets. fwiw, it's not like you're ever going to put the factory parts back on for warranty sake, and unless you moved or did something to the harness to cause it to chafe, the dtc set has nothing to do with the mods you've performed. Might just want to call the dealership and ask...no need to give them your personal information, just give them a hypothetical question about the work you performed and the dtc that's set and see if they say anything about it not being covered. Some dealers are better than others about working with you. The only down side is customer pay is almost always more than factory pay which gives them an incentive not to cover it if possible.
EDIT-
VCT solenoid resistance is listed as 5-14 ohms pp test HK4 (replace if outside spec)*
Voltage to the solenoid should be greater than 10.5v*
Resistance on the control circuits of the PCM connector to the VCT connector should be 5 ohms or less.*
Resistance from the VCT circuits to ground with PCM connector disconnected should be greater than 10 K ohms (essentially OL or infinite)*
Verify the PCM and VCT terminals are intact (not pushed in) and if possible do a pin drag test (I cant stress enough that if you perform a pin drag that you don't accidentally spread the female terminal and induce an open)*
If the control circuits show no short to ground, voltage, or opens, the solenoid resistance is in spec, it faults the PCM as the last test*
I wish I had a way to send you a wiring diagram, but I don't. This was using my 2013 as a model. The green wire which should be common to all the solenoids is B+ (hint, if you only have one solenoid code it shouldn't be a short to ground concern on the power supply. Still possible to have an open or spread terminal. Key on, engine off you should have B+ available on this wire at the solenoid connector). The other wire is the control wire from the PCM that turns the solenoid on/off by commanding ground. With the PCM connector disconnected and circuit at the VCT checked to ground it should be OL.
