2006 Avalanche service tire pressure monitor displayed

[rangrsfn]

Looking for help with an 06 Avalanche that displays "service tire pressure monitor" on display. If I reset TPS's, this corrects the problem for anywhere from 5 minutes to a day before the display reappears. I have also tried replacing all the tire sensors... A huge expense for nothing (I was assuming the batteries were going dead). No recent modifications have been done to the vehicle. When the problem occurs, any one of the TPS's or more than one will display "---". I'm thinking the rcdlr is bad. Just some background... I do not use the factory door lock remotes, I have a Viper auto start module with door lock controls..... This uses serial data via the BCM to communicate with the door locks. This has been working flawlessly for several years and was installed by me... No poor connections... All soldered. Also, the low tire pressure indicator is off..... If anyone had any thoughts or ideas... They would be greatly appreciated.