ive got a 96 camry 4cyl that has code p0401. i put vacuum on the egr valve and the car started to stumble, so that should be working correctly. i tested the resistance across the vsv and it was good. i was advised by the diag tech at work to replace the vacuum modulator and the vsv. so i did. the code is back.. and i dont know what to do now.

it has a new modulator and vsv. whats the next step

 

Not sure I can help. You replaced the VSV, a typically cause.

The link below has a good article on this code and the 5SFE.

http://www.motor.com/magazine/pdfs/092009_04.pdf

I would check all the vacuum lines for cracks, plugging, etc and correct installation.

Make sure the EGR valve is opening (engine stumbles) without needing a high vacuum. Its possible (and typically) for the EGR valve and exhaust gas tubing, etc to fill with carbon, the valve can also stick due to carbon build up.

Check the wiring to the VSV for damage, the ground point for the ground wire of the VSV for good contact.

Sometimes high back pressure caused by a plugged exhaust gas emissions converter can cause problems.

The link below has a good description for the system plus some diagnostic tests.

http://www.autoshop101.com/forms/h61.pdf

 

i figured it out today.. the egr was clogged completely


cleaned it out and all is good

 

Great!

Thanks for posting back with the fix!