I have a 09 CTS4 with Keyless entry and the only time I got “Electronic Key Not Detected” was when the fob had a weak battery. Replaced battery in both fobs at the same time and never had the problem again.
Note: buy good batteries, look at the expiration date.
I bought the car new 4 yrs ago this month. It has been a good car so far but only 25,000 miles. Summer catting around car.
