GM-41415-60 is required for leak testing of the Duramax diesel engine induction system. The tools rubber stopper fits into the air box and forms a tight seal. Using the previously essential GM-41413-A EEST/Smoke Machine, smoke can then be pumped into the system to test for and locate the source of any leak. GM-41415-60 can also be used for pressure testing, Fuel Tank Pressure (FTP) sensor validation and location of a leak in a capless fuel fill system. The tool fits and seals in the fuel fill neck and opens both spring loaded fill doors so the fuel and EVAP system can be pressure tested then filled with smoke to check for and locate any leaks.