P0400 won't go away
 

This code is irritating me. I've had the EGR cleaned out and the code still comes back. Any suggestions?

Other codes currently on: P0446 and p0136.

A plugged EGR tube is not the only cause of P0400. It could also be the EGRC solenoid valve or the EGR valve stuck closed or the EGR temperature sensor.

Here is a link to the service manual for P0400. I hope it applies to your car since you didn't provide details as to year and emission standards.

Start on page 254. http://boredmder.com/FSMs/Nissan/Maxima/1998/EC.pdf

The P0446 is the EVAP canister vent control valve, located on the EVAP canister that id behind the left rear wheel. These things get corroded from all the road water spray and stop working.

The P0136 is an O2 oxygen sensor. Which one it is depends on the year of your car and the emissions standards it was built to.

My apologies. She's a 97 SE 5spd with 122k, a NY car. Inspection is up at the end of Jan.

The o2 in question is the rearmost. I have a new one. There is exhaust putty around what's left of the old sensor and I'm not sure how to get it off.

If you can get a wrench on the sensor you can probably just twist it out, which will break the putty off. Otherwise you can try using a hammer and small chisel (1/4 inch). You probably wouldn't have to use that much force on it. If anything were to fall into the pipe, it won't hurt anything.

Worst case is that you replace that small section of pipe. It's just short piece of pipe that bolts on between the catalytic converter and the resonator. Junk yard sounds like a great place to get one.