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The engine genuinely running above its design temperature, which is recorded as a cause because it produces codes that name other things entirely. Detonation is the clearest example: hot combustion chambers ignite the mixture early, the knock sensors hear it, and the codes name knock on several cylinders while the fault is temperature.

Heat also changes what other sensors report. Intake air heated by a hot engine bay, oxygen sensors outside their calibrated window, and oil thinned beyond its rated viscosity all produce plausible readings that are not what the module assumes. So a cluster of unrelated-looking codes appearing together on a hot engine is usually one fault.

Treat the temperature as the finding and work backwards. Coolant level, circulation, the thermostat, the fans, the radiator's airflow and the head gasket are the routes, roughly in that order of likelihood. A temperature gauge is a poor instrument for this — many are damped to sit steady across a wide band — so read the actual coolant temperature in live data, where a genuine problem is obvious and a gauge shows nothing.