Powertrain Source reviewed Lights the check engine lamp

P04DE: Cold Start EGR A Flow Excessive Detected

Standardized SAE J2012 code · P04xx — Auxiliary emission controls

What does P04DE mean?

Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx. P04DE is the counterpart of P04DD: during an active cold-start strategy the flow of EGR A is too high – the strategy calls for little or limited EGR, but the valve lets more through. CARB requires separate codes for cold-start faults. No manufacturer document available to us uses P04DE; FCA uses the neighbouring code P04DD, so its use there is plausible but not documented. Too much exhaust in a cold engine causes rough running, smoke and in extreme cases stalling.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

  • Check engine light on
  • Rough idle after a cold start
  • Smoke or soot after a cold start (diesel), stalling possible

Common causes

  • High EGR valve not closing fully (soot, condensate, stuck open)
  • Medium Position sensor reports a wrong position
  • Low Air mass or pressure difference misreading

Likelihood is a general estimate across vehicles; your make and model may differ.

Add your car to see reports of P04DE on the same make and model first.

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