Ok This is Strange.
 

Looked out the back window earlier today and my truck was running, strange this is, I didn't start it. Truck does have an after market remote starter, is it possible someone else was able to start it? When I went out to shut it down I noticed that the CEL was on?

Colin

How long have you had the remote starter?

Was already installed in the truck when I bought it used, so at least 3 years.

Colin

I would think that few frequencies exist meaning it is entirely possible that although rare somehow you're vehicle started. Remember when garage door remotes were new technology and one could drive down the road and open another's door?

It's quite strange and scary too. Do update if this happens again. This might be because of the remote frequency matched with someone else remote.

Some aftermarket security systems can be set to automatically start and run an engine for a brief period if battery voltage drops too low.

Sent from my XT1080 using IB AutoGroup

Interesting but not sure if that's what happened, did drive the vehicle earlier in the day.

Colin

How did you tell it was running by looking out the window? Is it still cold enough there for vapor to show from the exhaust?
Maybe it is doing what VTX suggested and the problem is a failing battery. Would that throw a CEL?

Looked out the window and saw the lights were on (DRL's) Low to mid 70's here, will definitely check the battery though.

Colin

If your CEL was on did you read the code? That would be your best source of information as to what happened.