I use a Cateye double wireless CD300DW. I took my bike out for a ride in the cold and lost some functions - clock slowed down, etc.
Batteries were new. I tried a reset to change the time, and found that I could not synch the computer with the sensor. Replaced all 4 batteries, and tried all kinds of sequences to get them to synch - no luck. I followed the instruction manual to the letter.

What happens is you push reset on the computer and after the initial display, it blinks "Synch ID". At that point, you're supposed to push reset on the sensor with the computer in range, and the computer is supposed to pick up the sensor ID. All it does is continue to blink until it times out.

Does anybody have any suggestions?
Thanks!

I do not have any experience but reference this recent thread.
https://bikeforums.net/showthread.php?t=376570

Is the sensor and main unit in a warmer place when you are trying to sync, or are you outside in cold temps?

I'm trying this indoors where my house is 69 def F.

What if you spin the wheel when the head unit is seeking a signal from the transmitter? Perhaps it needs an active signal?

This has helped my Sigma computer to sort itself out sometimes. Other than that, I have no idea...

I presume you have tried removing the head unit and holding it a few inches away from the wheel sensor when trying to sync?

If that doesn't work, I'ld guess it's time to contact cateye.

Other ideas:

1. have you reset the wheel sensor, I think it's a 5 sec reset
2. have you downloaded the owners manual from cateye
3. don't forget you can reset the main unit
4. finally, you could try reformatting the main unit.