Car Won't Start — How to Find the Cause
The key to diagnosis is what happens when you turn the key: slow cranking, clicking, silence, or cranking with no fire — each points to a different cause.
Slow cranking or clicking
Usually a weak battery or corroded battery terminals. Dim lights when trying = battery. Rapid repeated clicking = a dead battery or weak starter.
Total silence at the key
Could be a breaker/relay, a disconnected battery terminal, the ignition switch, or an immobilizer not reading the key. Check the dash lights.
Cranks but won't fire
Fuel (pump/filter), ignition (plugs/coil), or the crankshaft position sensor. This usually stores a fault code — read it via OBD2.
FAQ
I only hear clicking — why?
Most likely a dead battery or weak connection; try a charge/jump. If it starts after, suspect the battery or alternator.
Does OBD2 help if it won't start?
If it cranks but won't fire, yes — it often logs a code. If it won't crank (battery), an electrical check matters more.