Cause
Sensor connectors swapped during repair
Two identical sensors whose connectors have been interchanged, so each reports accurately from the wrong position. Every individual test passes — the sensors work, the circuits are sound, and the readings are plausible — which is why this survives a complete diagnostic.
Only the comparison between positions reveals it, so the codes are correlation and rationality faults rather than circuit faults. A correlation code on a system that was recently opened, with two sensors of the same part number, is this until ruled out, and it is far commoner than a genuinely drifted sensor.
Exhaust temperature sensors are the classic case, since a modern diesel carries three or four identical units differing only in lead length and position. Oxygen sensors across banks are the other. Compare each reading against what its stated position should show — a sensor reporting a temperature that belongs further down the exhaust is telling you where it actually is. Check the routing against the diagram rather than against how it looks, because a swapped pair looks entirely normal and the lead lengths often permit the mistake.
Typically an easy fix. Often worth checking before paying anyone to look.
Codes this can cause (3)
Codes where this is a likely explanation first, rather than merely a possible one.
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