MAP sensor plug test
 

Locate your MAP sensor(s), they are on the rear of the engine above the rear valve cover. The plug(s) are on the rear and point down.
https://www.gmforum.com/howto/test-pics/PA010010.JPG

Lift on the tab, wiggle and push down. Do not pull on the wires. Check plug for corrosion or damage. Clean or repair if needed.