DTC stands for Diagnostic Trouble Code — the standardised fault codes an ECU stores when a monitored system operates outside its target values. For deactivation orders these codes are relevant for a simple reason: they show us exactly which monitoring functions the ECU already has active, which monitors have already triggered, and whether there are existing hardware faults that need to be accounted for in the software solution.
An example: a DPF-Off order arrives with no DTC readout. We build the file based on the original. The vehicle comes back — P0401 (EGR underfunction) was already active before the DPF issue and reappears after the remap because the EGR monitor is still active. With the DTC readout, that would have been addressed in the file from the start.
For DPF-Off: all P2xxx codes (particulate filter differential pressure, load faults, regeneration faults), exhaust temperature fault codes (P0544, P0546, P2080 etc.) and DPF soot sensor codes if fitted.
For EGR-Off: P0400–P0409 (EGR flow faults), P0489/P0490 (EGR valve control), EGR temperature sensor codes, and — important on newer vehicles — P0401 (EGR underfunction after learned value).
For SCR/AdBlue-Off: P20EE (SCR NOx catalyst efficiency), P2BAD–P2BB1 (AdBlue quality), P203A (reductant level), dosing valve faults (P20F5, P20FA), and NOx sensor faults before and after the SCR catalyst.
Seemingly unrelated codes can also be important: a P0299 (boost pressure underrun) alongside a DPF problem often indicates already elevated exhaust backpressure — this affects how aggressively we adjust the smoke limiter after the DPF-Off.
Please always submit the complete fault memory — both active and stored (passive) codes. A stored code that is no longer active can still show that a specific monitor triggered in the past and is still being watched. For deactivation orders, both states are relevant.
Even better: the fault memory before and after a clear attempt. Codes that immediately return after clearing are active faults with an ongoing cause — that is a different starting point than a stored fault that hasn't reappeared since the last workshop visit.
When submitting an order in the ecufiles.io portal, there is a free-text notes field. Simply enter the relevant codes there — either as a list (P2002, P0401, P20EE) or attach a screenshot from your diagnostic tool.
No diagnostic tool available? The readout report from your flash tool (KESS3, Autotuner, CMD) also includes a DTC overview for many vehicles. That is perfectly sufficient as a basis.
In short: the more information included at submission, the more precise the file — and the fewer follow-up questions or revisions needed. Two minutes of diagnosis can save another workshop appointment.
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