Not sure I understand your post entirely, but cags is not designed to keep you out of second at all rpm's, it just locks, or rather makes the transition from 1-4 more natural. It is designed to do this if and only if certain conditions are met (I.e. Proper acceleration speed, rpm's)
If yours is no longer working either it has gotten turned off in the PCM, or the solenoid has gone bad. PCM requires a tuner, solenoid replacement would be abut more involved
Are you sure that you are driving in the exact conditions that should cause CAGS to work? I guess I am wondering if you have seen the "1->4" indication in the speedometer and then CAGS did not work, or have you just not noticed CAGS lately and you think it is broken?
I believe that transmission temp is one of the requirements for CAGS to work, was you car warmed up when you tried it?
It sounds like you need S-CAGS - Super Computer Assisted Anti-Gforce-Selector. It's designed to prevent you from accessing gear ratios that might generate too many G's while accelerating. It's about $5.00 on ebay, but make sure you get one with the right harness for the V - don't make the mistake I did and pick up a Camaro S-CAGS.
Damn...what a coincedence. My CAGS eliminator actually failed yesterday on April 1st. SES light came on and OnStar operator said "Skip Shift" is not operating properly. I think the resistor just burned out. Seen other people post about it. Skip shift still eliminated, just have that damn SES light.