I's a problem with the EGR system and or the EGR solenoid.
It all depends on the production date of your Maxima. Federal emission Maxima 06-2000- 06-2001 are EGR delete.
The EGR valve is bolted to the rear cylinder head at the transaxle end
Code P1400 means EGR solenoid valve or circuit fault
see the egr valve location on the 1999 Nissan Maxima-it should be very similar.
Under throttle body
See graphic, don't confuse with EGRC-BPT valve. http://img.photobucket.com/albums/v158/evilBIGD/EGR/vacuum.jpg
The EGR valve is bolted to the rear cylinder head at the transaxle end
There isn't one.
The EGR valve is bolted to the rear cylinder head at the transaxle end
The EGR valve is bolted to the rear cylinder head at the transaxle end
The EGR valve is bolted to the rear cylinder head at the transaxle end