Cause
Failed coolant pressure cap
The pressure cap no longer holding its rated pressure. Pressurising a cooling system raises the boiling point of the coolant — that is the cap's entire purpose — so a failed one lets the system boil at a temperature it should handle easily.
The symptom is coolant loss with no visible leak, since it boils off through the cap, together with overheating that appears only under sustained load. It is the cheapest part in the cooling system and the first to eliminate. Test it on a pressure tester against its stamped rating rather than by eye; the seal hardens and the spring weakens invisibly. A cap that vents early also draws air in as the system cools, which is how an air lock forms in a system nobody opened.
Typically an easy fix. Often worth checking before paying anyone to look.
Some of these codes mean you should stop driving
1 of the 1 codes this can cause indicate a fault where continuing to drive risks damage or is unsafe. Which one you have matters more than the cause does — read the code's own page before deciding.
Codes this can cause (1)
Codes where this is a likely explanation first, rather than merely a possible one.
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
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