engine codes - Diesel Forum

twister01 · 07-10-2009, 11:49 AM

My truck threw a cel with two codes PO401 , PO404 and the next time i tried to start it it ran @high idle and then turned real ruff and died ! now it won t even start.Any Ideas besides my wifes = buy a cummins/duramax! thanks Dave

southarkems@sbcglobal.net · 07-14-2009, 10:20 AM

check the crank shaft or cam shaft sensor

rcgreg · 07-14-2009, 01:07 PM

I believe those are EGR Codes - check the EGR valve

onyx · 07-14-2009, 05:26 PM

Don't no if this helps but I have codes P0401 which is EGR insuff. flow and P0402 which is excessive flow.

djshum · 07-14-2009, 06:31 PM

those are egr codes, you probably have a stuck valve. You can try cleaning it, but it is a 50/50 shot that it will cure your issues. If you still have issues after cleaning, you will need to replace valve. Pull valve out and inspect. It is probably stuck open.

onyx · 07-14-2009, 06:55 PM

I just took my valve out tonight and it looked ok, wasn't stuck open. I cleaned it and it did nothing. Does this mean the next thing is a new one?

djshum · 07-14-2009, 07:22 PM

Most likely will need a new valve. That is my best guess, based on codes you've given and not actually diagnosing it.

djshum · 07-14-2009, 09:23 PM

My posts were for original poster, with my last post thinking onyx was original poster. Onyx....I have seen intake temp sensor cause insuff. flow codes due to carbon deposits on sensor. The carbon insulates the thermister and the voltage doesn't change as quickly as it should setting code. It is located on LH side of intake near front. Remove it and clean it, may be all that is needed.