There is a Gm doc.
01-06-04-018A: Intermittent Malfunction Indicator Lamp (MIL) and PCM DTC P1404 (Recalibrate PCM)
You'll have to get that done at the dealer most likely,
but also I have seen where the EGR port going through the intake manifold gets clogged.
And it is possible that the EGR is not performing as it should, did you buy it from a dealer or auto parts store?
Wednesday, February 24th, 2010 AT 9:11 PM