Had a 2015 Freightliner Cascadia throwing a cylinder 4 misfire code last month outside Tulsa. Shop wanted to pull the injector, but I checked the fuel return line first and found a cracked O-ring under a loose clamp. Replaced the clamp and the O-ring for under $10 total, cleared the code, and it's been 600 miles with no return. Anyone else ever dodge a big ticket by checking the cheap stuff before tearing into the head?