Starting car with left turn signal...

[MCF34]

Yep...

You are describing an aftermarket kill switch (alarm system). After hitting the unlock button on the remote and turning the alarm system off you can start the truck normally, but the reason why you cannot start the truck after sitting in it for 30 seconds is because the alarm system resets itself and activates the kill switch.

There are many ways to wire the truck with a kill switch, some by pushing in the cigarette lighter some by turning a switch on and in your case, turning the turn signal on. I personally would have wired it to the heated washer fluid switch.

I'm curios to know if the kill switch is a OEM product, aftermarket like a CrimeStoppers or Clifford and if its operated from the OEM remote or an aftermarket one.

To show it is a kill switch do this:

Put driver window down

Get out of truck

Press the "lock" button on the keypad

Wait 1 minute

Without touching the unlock button on the keypad reach threw the window, put key in the ignition and try to start the truck

The truck shouldn't start and the alarm should sound.

That sounds about right...I will try your test tomorrow, but to answer your question, it is the stock GM remotes that are used to lock/unlock and remote start the vehicle. One remote sets all the memory settings to my preferences and the other sets all the memory settings to my wife's preferences.