Have a cadillac deville with a 4.6l northstar vin Y. The vehicle doesn't want to kick into reverse anymore. Sometimes out of no where it will kick into reverse though. The vehicle does drive smooth in drive. I did change the transmission oil and filter not to long ago. Any ideas on what it could be? Pls and thank you

You need to scan for transmission codes it could be a solenoid sticking that can be repaired by pulling off the transmission side cover