Trouble shooting code

The fault is somewhere around the EGR valve - probably the EGR valve or the throttle position sensor.

Before replacing any sensors try removing and cleaning the EGR.

Here's a Youtube link that may be of help to you:

1999 maxima egr Google Search

This link explains about the EGR:
P0400 Exhaust Gas Recirculation Flow Malfunction

CEL code P0400 EGR Flow Malfunction

p0400 ,is EGR monitor failure. OBD2 tech.
the ECU does 2 tests, each driving cycle.
yours fails,
the EGR on suz are a 50k service check, didn't clean it yet?

Google the codes

Lots to read & study

OBD2 PO401

OBD2 PO455

Think you will a repair shop to smoke the
Evap for the 455

P0422--Main Catalyst Efficiency Below Threshold (Bank 1)

Worn out Exhaust Converter

They need to be replaced at 12 to 14 years,
even if they pass inspection,at that point they
no longer are doing much

You can get any codes you want by using google
& entering OBD2 Codes & your codes & can include
your veh & year in case you get euro,asian or domestic
conflict on a code

P0400 code is for EGR(engine gas recirculated) flow malfunction.
need to clean EGR canister.

After you have made the repairs go back to Advance Auto and have them remove this stored trouble code .Most places will remove them from your computer for free.

Well the check engine light flashes as part of your OBD2 technology that in the vehicle what you do if you can is count the number of times it flashes, that number is what technicians refer to is the manual trouble shooting code tells them without having to hook up a scanner what system or part is going wrong in the vehicle. if it flashes when you put it into passing gear it could have something to do with your tranny or possibly even your gear box. if you have the code number you can usually look it up online by going to google.com entering the year of your vehicle followed by OBD2 trouble code number "then insert the number of times it flashed before going off completely"

Post the codes here and we can help you define them, or paste this link into your browser window and bookmark the page - it's an OBD2 (1996 and newer) fault code list that you can use to look up the codes:

http://www.obd-codes.com/trouble_codes/

Just click on the brand you're concerned with, and have at it:)

the passage that causes this low flow is in the intake, it gets full of carbon and gunk, try running a wire through it, also make sure the EGR passes a functional test.

this is an OBD2 car and you will need a scan tool to find your code
there are many auto parts stores that will do it for free