Cause
Debris or damage to the radiator coating
Damage to a radiator or condenser's surface treatment, including the catalytic coating used on some vehicles to convert ozone as air passes through. Those coated radiators are a genuine emissions device rather than a cooling one, and their efficiency is monitored — which is why damage to a coating produces a stored code at all.
The coating is thin and sits on the leading face, so stone impact, pressure washing at close range, and corrosion from road salt all remove it. Aggressive cleaning is a common cause, and worth mentioning: a high-pressure lance held close to a radiator flattens the fins and strips the coating in one pass.
The module infers efficiency rather than measuring the coating, so the code is a calculated conclusion and other faults reaching that calculation will produce it too. Inspect the face for flattened fins, corrosion and bare patches before accepting it, and check that airflow through the matrix is genuinely unobstructed — a blocked radiator reduces the same efficiency the coating is being blamed for.
Typically a moderate job.
Codes this can cause (3)
Codes where this is a likely explanation first, rather than merely a possible one.
Information, not instruction
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