P04DE: cold-start EGR excessive flow compares modeled and measured air mass

P04DE describes excessive EGR flow during cold start. In Audi's CPNB chart, the criterion compares a ratio of modeled and measured air-mass flow with a limit that depends on turbocharger position. The model, measurement and operating position are therefore all part of the documented evidence.

Excessive flow is an inferred system result

The row does not state that the controller directly measured an EGR valve physically stuck open. As diagnostic interpretation, an abnormal air-mass relationship needs explanation through the relevant system checks; the code alone does not isolate the valve from the information used to evaluate flow.

Turbocharger position also prevents the limit from being treated as a single constant. Comparing observations from different positions without the applicable calibration could misrepresent what the controller considers excessive.

Retain cold-start conditions

A normal reading after warm-up does not reproduce the situation named in the fault. Preserve the available cold-start event information and identify the correct CPNB diagnostic procedure. Audi's quick-reference row does not publish the full ratio function, a numeric universal threshold or a mandatory repair. This is a scoped explanation of the monitor, not permission to apply another engine's airflow target to P04DE.

Source: Audi 2014 A6/S6 Quick Reference Specification Book.