How can I check for an evaporative emission leak in a GMC vehicle?

Answer by  doc325 (454)

To check for an evap leak on a GM car you need a scanner.Once the system is sealed you can put smoke into the system and see where it leaks.

Answer by  hypertech (690)

Professionals will use a smoke machine, but for a home mechanic all you can do is physically inspect fuel cap, solenoids, charcoal canister and all connecting hoses inch by inch. The most common issue is a bad fuel cap, but also look out for cracked hoses, melted purge valves, or stuck vent solenoids.

Answer by  leroy (231)

You need to take it to the dealer, they have a tester that's pressurizes the system to check it. Also need to be able to access the computer to do so. Check your gas cap first, usually that code is set with a loose cap.