If you are investigating coolant loss noticed after highway driving, save every stored and pending code before clearing anything. Save temperature-related codes, but do not treat their absence as proof there is no leak. Record the engine temperature and load alongside the reading; the same value can mean different things in different conditions.
A basic reader may not access every module. Inspect visible hoses and the reservoir for traces; a leak may only appear under pressure. Use the exact vehicle’s service information to interpret the result.
Quick educational note
For information, not a diagnosis or repair instruction. Vehicle-specific checks are still required. Consult the manufacturer's guidance and a qualified technician.
How to use this information
This article explains general principles and does not establish what is wrong with your vehicle. Read the content limitations.