Check engine light comes on my RX300 periodically; odometer has 136,000 miles. Had AutoZone diagnostic reading done while light was on. It shows troubleshooting Code P0768. Definition: -Shift solenoid "D" electrical malfunction - SSV S4. Probable causes: 1)Open or short circuit condition, 2)poor electrical connection, 3)failed SSV S4 as probable cause. The car runs fine, with a light clicking sound coming from area behind radiator. Could this be a major repair problem? Should I take it to a Toyota or Lexus automotive repair shop?