07 GMC Sierra

[Feltonm]

What is causing my 07 Sierra to stop running when it rains hard

[Jsdirt]

Could be any one of half a million things. Electronics, no doubt ...

[Doug_Scott]

If you have no idea where to start, try using a garden hose and soak various sections to see what creates and issues. Try soaking the area around the fuel tank first, paying attention to the connections for the fuel pump on the top of the tank. Does it set any codes when it quits? Does it quit while driving, or does it just become a no start under high humidity?

Suggest you check for the same things you would do for a pre-computer engine, spark and fuel.