Write-ups from the manuals and the garage. Every one starts with the symptom, works to the root cause, and tells you what to check before you spend anything.
Before you touch the engine, look at your dashboard. If the ABS light is on too, you have one fault — not two — and it's probably a one-dollar fuse.
More write-ups in progress — W201 hot start failure, E30 rough idle, and Motronic diagnostics.