Should I start with egr valve replacement or should I also replace MAP sensor and vacuum modulator.

 

P401 Exhaust gas recalculation flow insufficient detected. The engine is not getting enough recycled gas from the EGR system. Causes could be stuck closed EGR valve, defective EGR VSV, or MAP sensor, and EGR vacuum hose leaks. The actually EGR valve or the gas tube running to it may be plugged with carbon up.

Would not replace the MAP if engine runs OK.

Does the engine run OK, if so the EGR system is not stuck open othewise the engne would idle rough.

The EGR valve may be plugged with carbon or the VSV valve not working to allow engine vacuum to the EGR modulator which controls how much EGR valves opens.

You can also check the VSV valve by applying 12V and determining if it opens and closes ok or should have guessing a 15 ohm electrical resistance.

The EGR valve can be taken apart and cleaned along with the metal exhaust tube running to it.
Basically the VSV valve (controlled by computer) turns the EGR valve on/off by controlling vacuum to the EGR diaphram. The modulator valve is connected to the engine manifold and reacts to manifold pressure. It is also connected to the EGR valve and controls how much the valve opens based on manifold pressure.

Also check for leaking vacuum hose in the system..

 

I was getting codes Po401,po441,po446.
[/align]I paid to the mechanic.He took out EGR valve and cleaned egr valve and its tubing with spray and then pressure wash.He put it back.After one day i did not get the codes po441 and po446 again but i got new code po401 ??Please let me know what is it.My gas cap is tight.Do i need to replace with new gas cap or should i replace the Exhaust drum on back of my Camry-2000,4cyl, 150000KM .
[/align]I wanna do it myself.Please let me know the exact location of part need to be clean or replaced on front side??

 

Replace the EGR Valve, Vacuum Modulator, and Vapor Pressure Sensor. One at a time if you want but its difficult to track down which is sticking. All of them are full of carbon deposits and should be replaced.

 

Thanks alot.I will dothat next week.
Do you have an idea about the price of ,EGR Valve, Vacuum Modulator, and Vapor Pressure Sensor.. Today morning i got the light back and am getting three previous codes, PO441,PO446,Po401.
I saw a sonsor behibd EGR valve in my Camry2000.It say" Toyota , Sensory Assay , VAC, 89420-060 40 and at the bottom is a number, 0136 .
Please let me know what is this sensor about and Do I need to clean it or replace it also if it may be causing the problem ???

 

I'm getting the 0401 code as well, have been for quite a few years now actually. I haven't noticed any thing weird going on, not excessively rough idle and still get ~24 MPG combined. Should I even bother worrying about this? Is it going to eventually hurt my engine?