DTC P0768: Reduction Timing Solenoid Valve Circuit Fault (Open/Short): Description
WARNING: This page is about a different car, the 2002 Mazda MPV. However, it is still accessible from the selected car via links, so may be relevant.
Open or short in reduction timing solenoid signal system (while TCM monitors solenoid output voltage, the voltage that differs from the ON/OFF signal output by CPU in TCM is detected).