Edit: I added this to my site with other DIYs which can be found here:
The following fault code was causing my CEL to come on. I would clear the code using my VAG-COM but it would come back within a short period of time.
17704 – Error in Mapped Cooling System (usually temp sensor or thermostat)
P1296 – 35-00 - -
I went to the dealer and purchased the updated temperature sender (green-top) for about $13 with a new O-ring ($2)
OLD -Temperature Sender (Black)
NEW/Updated - Temperature Sender (Green)
Before beginning this procedure, ensure you allow your engine to completely cool down. The system is pressured and if you remove your temperature sender while it is still hot, coolant will spray out and potentially cause severe burns.
WARNING: This procedure was performed on my 2001 Volkswagen Jetta 1.8T. I cannot gaurantee this will work on your vehicle. Work at your own risk. It took me about 5-10 minutes to complete this.
Step#1: Remove the upper and lower engine covers to allow easy access of the temperature sender.
Step #2: Remove the retaining clip that secures the temperature sender in place. Slide the pick into the small portion of the clip that can be seen. (between the plastic housing and edge of retaining clip). Pull the clip straight out with minimal force.
Step#3: With the clip removed pull the temperature sender out. Unplug the 4-pin harness.
Step#4: Plug the new temperature sender (green) into the 4-pin harness.
Step#5: Insert the new sender and be sure to press it in firmly.
Step#6: Slide the retaining clip and ensure it is securely seated.
Step#7: Install the upper and lower engine covers.
That’s it! If you have any questions feel free to contact me via EMAIL, PM, or IM.