My scion xb has a pcode 301. Changed spark plug and coil. What else is it?

Hello, Dave here, contributing to RepairPal and providing expert advice since 2010. Before replacing anything, it would have been helpful to check the coil and plug by swapping each with a known good plug and coil from other cylinders. Different ones. If the misfire returns, is it the one where you put the coil? The plug? Or is it the same cylinder 1 misfire? Now that you've replaced parts -- i'd still probably do that. Do you know your new coil and new plug are OK? If compression is good, then i don't suspect base engine. A shop near you can aid in the diagnostic process -- https://repairpal.com/auto-repair-near-me Click the link or call us at 877-913-1554. We'll gladly find you a certified RepairPal shop in your area.