✅APPLICATION -- Replaces CUMMINS Tool Number 3164001. Works on Cummins ISX, Cummins Signature Engines. Replace OEM Cummins Tool Number 3164001. Fit for Cummins ISX, Cummins Signature Engine. ✅FUNCTION -- This test checks for combustion gas leaks back through the injector rail check valve or other conditions that will allow gas leakage through the injector into the fuel rail.