What is the location of the cabin air filter in a 2013 Express 1500 van

 

There isn't one. If your vents stink then spray some lysol into them, and into the cowl with the fan on full.
Also clean out the evaporator core as it tends to grow mildew in some climates.

 

I wanted to ask that question and answer. If a person wanted to, I suppose they could add one. That must be possible. To customize something. As a project, I'd love to add a drip with a drip line feeding it from a tiny pump. Every time the start position is selected or perhaps on a timer in the run position, the pump activate and pulls air freshening fluid from a reservoir feeding the sponge sitting in an air duct. Viola. Automatic Air Freshener. They sell cans of almost self evaporating jello. I dropped it down the air vent. Worked well. With what they charge for those little cans, I am looking at about $5 per week. There must be a cheap way to make your own freshener and doing something similar to what is posted.