I have a 2003 A^ 2.7turbo for a month now. A week ago, I noticed some transmission issues while driving in heavy rain; all the TIP gears lit up and I could only drive in one gear. Afer engine was turned off for a short while, everything operated normally. Today, it happened again while driving but now the CEL light is ON! I went to the local auto parts store and had the code printed. It's and DTC (P0763) code - Shift SOlenoid C, Circuit Electrical.

It appears that when it's dry, no problems; when it rains, the TIP slips. How critical is this problem and any idea how much it'll cost to fix it? Please send ideas. Thx.