⚡ TESTING GM 4-Pin HEI Ignition Module, both on the bench and in the car. If your engine’s cranking but won’t fire — this is the first thing you should check. ✅ Power ✅ Ground ✅ Coil Negative Switching If it ain’t switching — it ain’t sparking. #IgnitionTrouble #NoSpark #HEIModule #GMTech #CarWontStart #DiagnosticsDoneRight | My Mobile Mechanic / Auto Repair & Brake Replacement.