Diagnostic article Generic OBD-II
P240F: EGR slow response is evaluated using changing air-mass targets
Audi's CPNB P240F monitor uses calculated characteristics tied to positive and negative target-air-mass gradients, rather than one static EGR reading.
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Documented application
Audi 2014 A6/S6 Quick Reference Specification Book, September 2013, Engine Code CPNB, DTC chart. Thresholds only describe this documented monitor; not universal across other makes or engines.
The code alone does not identify a failed part or establish that a vehicle is safe to drive. Confirm the vehicle, reporting module and applicable service procedure.
P240F identifies slow EGR response. Audi's CPNB chart describes calculated characteristic values associated with negative and positive gradients of target air-mass flow. The listed boundaries are greater than 35 for the negative-gradient characteristic or at least 30 for the positive-gradient characteristic, with dimensionless notation.
The response is dynamic
A gradient describes change, so this entry should not be reduced to a fixed airflow value at idle. As diagnostic interpretation, an acceptable static reading does not independently demonstrate that the system responds correctly when the target changes. The direction of change is also relevant because the table lists different characteristic boundaries.
Those numbers are not seconds, grams per second or a permitted EGR opening percentage. Converting them into a familiar unit without the calculation would invent a specification.
The chart is not the complete algorithm
Audi does not publish the full characteristic calculation or isolate the failed component in this row. The correct CPNB diagnostic procedure is needed to connect the dynamic fault to its cause. This article explains why changing target-air-mass evidence matters, without claiming that P240F proves a mechanically sticking valve or supplying a universal response-time test for other engines.
Article source documents
Source checks describe how the text was prepared; they do not certify a diagnosis or confirm compatibility with every vehicle using this code.
Original code reference
Dictionary definition
EGR Slow Response
This definition retains its original catalog scope. The article above is limited to its explicitly documented application.
Reference scope
Generic OBD-II definition.
A manufacturer label does not establish the model, year, engine or module to which a diagnosis applies. Read the safety and diagnostic limits.
Separately researched
Vehicle-specific diagnosis
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Definition source
- DTC Database: pinned community code definitions
Source checked · MIT