I have a 2007 1LT, RPO AP3 code on my label (matching VIN) but, whenever I program a remote start fob all it does is flash the parking lights when trying to start from the remote.

 

Are you following the correct remote start proceedure?
Check your owners manual.
Lock, Lock, Start.

 

An CEL light ?
are the brake lights working?
is the hood closed?

as mentioned, press the lock button twice , then press and hold the start button for a few seconds.

 

Most important is RS enabled in the DIC?
Any Check Engine Light?
If these fobs are not Genuine GM they might not work. If the circuit board has a LED on it, probably won't work.

 

Definately.

No CEL (I know GM's won't RS with a CEL light on)
Brake Lights work
Everything is shut.
The proper sequence is followed and just the parking lights flash.

I don't see the option in the DIC, I don't remember if I saw the option in my '06 either and it had RS. I'll search more tomorrow.
I do have 1 genuine GM fob and it does the same thing.

 

Read thru the owners manual to ensure the option is selected in the DIC , there’s a link in Donbrew’s signature

 

If the option is not there you don't have it. Look at the hood latch, does it have an electrical connection to it? Not the impact sensor behind it.
AP3 does not mean RVS in all years. It actually means it has a RCDLR for 2007. Other years it means hood latch switch installed. If it was a rental in a former life, it is likely ordered without.

 

Has the RS ever worked ? If not, then Don is probably correct that your car doesn't have it.

 

Not really sure. I picked this up last week and it only had the standard Keyless Entry Fob.

 

I got it figured out!
It was turned off in the DIC...... Now I'm going to program the other remotes and see how that goes 👍👍

Got all 3 (2 RS & 1 Standard) programmed and working just fine now.