2002 V40 Volvo with a code P0015

I have a 2002 V40 Volvo, 2 months ago the code P0015 star appear, I took it to the mechanic and he change the CVVT hub, which is driven by the timing belt on the end of the camshaft, Also he replace the water pump and the timing belt with the pulley's, for a second the Check engine light was gone, in order to fix the problem I buy the Variable Valve Timing intake camshaft Solenoid valve and I replace it, also the Camshaft Position Sensor, was replaced, after all this investment the code P0015 still coming out any fed back in how we can fix this problem?

Thank you
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