I think the low oil pressure sender is the only alarm input that changes with higher rpm, since oil pressure increases with throttle. Check your engine dipstick and oil pressure gage at idle. If the oil level is good, check the sender and gage connections. If good, (gulp), you may have an oil pressure problem. Hopefully and old, dirty or collapsed filter that is working in bypass.
Else put a 0- 100 psi gage into the sender port and check your oil pressure. My 4.3LX manual says 4 psi min. @ idle, 30-55 psi @ 2000 rpm. I can't imagine a 2012 engine not meeting these requirements. If the engine tests good, time to test the sender's ohm/voltage output, and hopefully just need to change this.
ps.: After another cup of coffee I thought of a possible shorter diagnosis. If your dash gage shows good oil pressure at idle while the alarm is sounding, I'd move the low oil cut out switch up the list of suspects. This is a normally open switch that closes once the min. oil pressure is sensed. You can test this by pulling the two spade connections off, and jumping them. If the alarm stops at idle, I'd feel safe spending the $$ on a replacement.
