Last winter a Civic came in with intermittent no-crank. Owner already had a starter in the cart for $340.

Battery tested 12.6 at rest. Starter was fine. The negative cable looked clean at the terminal — and was green and cooked at the block. Voltage drop on that cable during crank was over a volt. Four-dollar terminal, twenty minutes, car started like it was embarrassed.

This is the whole job.

A code is not a part. A click is not a starter. A shop estimate is often a guess you are paying them to make because you skipped one test.

If you work on your own car, write the complaint down, test the cheap thing that can fake the expensive thing, then buy the part. Torque what you touched. Put it on stands, not a jack.

That is the WrenchLab loop. Diagnose the noise. Follow the procedure. Skip the shop bill — when the test actually says you can.