Two questions: Check engine code mystery, and contaminated engine coolant
2003 Ford Ranger, 2.3L 4 cyl. 2WD reg. cab, w/AC. 137,000 miles Model so plain it doesn't appear on any list. 1st question: Why do I get a "cruise control circuit open" code when I don't have cruise control? 2nd question: Engine coolant looks extremely contaminated after overheating (pegged the guage twice) while towing a small, but over recommended weight, trailer for 650 miles over 17 hours, with stops to cool off. Unsure if contamination started before overheating. Coolant is dark, rusty, with some sheen of oil, no droplets. Coolant was flushed and replaced one year ago. Blown head gasket? Warped head? Other possibilities? Is a definitive diagnosis possible? Truck overheats now just slightly, and only when under some load, like going up long hills.