Why does code P0401 keep returning?

Question

I've replaced the EGR valve, the DPFE sensor and the EGR vacuum regulator.  I've disassembled and cleaned then ports from the EGR to the intake.  If I apply vacuum to the EGR valve, the engine stumbles as it opens.  The vacuum lines seem to be ok.  Does this mean the PCM is defective or is there something I'm overlooking?

Answer 1

It is possible the pcm is causing the issue, however you also need to check the electrical connections and map/baro sensor.