P0400 code on egr system for 1999 Nissan Maxima with 3.0L engine.

Question:

I have this P0400 EGR malfunction in this vehicle and following ATS past newsletters, I have serviced the egr valve and verified integrity of the vacuum hoses and blew the egr passages. However, after resetting the code, it came back after 3 days of driving. Did I miss anything on fixing this code? Is it possible that the ecm (engine computer) itself is no good?

ATS Adviser:

Your ecm should be good but there is a possibility that you have not really cleaned the egr passages thoroughly because this job needs the removal of the top plenum in your engine. There is a tube there that contains the egr signal to the ecm to monitor the egr system. Anytime, that passage is blocked, your ecm will store an egr fault code. You can test this by running your engine at idle and lift with your finger the egr pintle shaft of the egr valve. This should make your engine quit, otherwise, the passage itself is clogged.

ATS Tip:

While you are doing this, you can also check the integrity of the egr valve which could be stuck closed including the egr temperature sensor voltage. Finally, a weak battery can also cause this code which is very common. Please contact ATS for further details.