Cause
Genuine exhaust over-temperature during regeneration
Exhaust temperatures genuinely running above the expected limit while a particulate filter regeneration is in progress — a real condition rather than a sensor fault, and the module is protecting the aftertreatment by reporting it.
Regeneration deliberately runs the exhaust hot, several hundred degrees above normal, by injecting fuel late or into the exhaust. So a high reading during regeneration is expected and only becomes a fault above the protection threshold, which is why the code names the condition and the timing together.
Two things push it over, and they lead to different repairs. A filter carrying more soot than it should releases more heat when that soot ignites, so an overloaded filter overheats its own regeneration — the cause is the loading, not the process. Or fuelling is excessive: a leaking or coked exhaust injector, or an in-cylinder strategy delivering more than intended. Check the soot load recorded at the start of the regeneration: a high load explains the temperature and points upstream, while a normal load with excessive temperature points at the fuel being added. Aborting regenerations repeatedly makes the first case worse, since each abort leaves the load higher than before.
Typically specialist work. Needs equipment or training most home workshops do not have.
Codes this can cause (4)
Codes where this is a likely explanation first, rather than merely a possible one.
- P244D Exhaust Temperature Too High For Particulate Filter Regeneration Bank 1 Likely for this code High
- P0546 Exhaust Gas Temperature Sensor Circuit High — Bank 1 Sensor 1 Moderate
- P0549 Exhaust Gas Temperature Sensor Circuit High — Bank 2 Sensor 1 Moderate
- P226D Particulate Filter Deteriorated/Missing Substrate Bank 1 High
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