Another P0401...Replaced EGR Valve, Vacuum Solenoid and Air Intake Hose!

[corrinebean23]

Stiiiiilll getting the error code. Replaced the EGR Valve, vacuum solenoid, and air intake hose now. Throttle body is as clean as a whistle.

What else could it be?!? Valve position sensor? Or still maybe just the hoses that connect to it?? They seemed ok, but I didn't pay them a ton of attention when I was replacing the valve & solenoid.

[Maim Menu]

You might want to check out these two links with possible fixes

http://www.automotivehelper.com/topic515169.htm
http://www.automotiveforums.com/t309...401_p0402.html

Tell us if that works so we can try something else

[Eye8Pussies]

like you said about the vacuum hoses- double check them- the valve needs a decent bit of vacuum to open.

If you have a cracked hose or if your hoses aren't connected properly according to the toyota vacuum diagram, the valve may not open like it should.


I had vacuum going to my egr valve on my solara and it was correctly hooked up the the egr vsv, but I had my vacuum hoses to the vacuum rail hooked up incorrectly and there wasn't enough vacuum to open the valve. After I fixed the vacuum hoses to how they were supposed to be, no more code.

It's definitely worth taking a look

[fenixus]

best idea would be to take a pic of your hoses routing, compare it with the diagram and then removal one by one. check each hose for:
a) restriction by blowing air through it
b) leaks by trying the hose to hold vacuum with a mityvac (and plugging the other end with a finger). they should hold high vacuum (up to around 25inHg) for at least 30 seconds.
c) inspect for any visual symptoms of aging, cracks, cuts, punctures, collapsing under vacuum etc.

double-check is an important term here. i missed one leaky hose at first check. when double-checking i found it out one of them (going from modulator to the vsv) is slowly leaking vacuum, the faster the hotter it gets.

also, did you try checking if the VSV gets voltage to operate ? if your VSV is same type as mine, then there is a confusion about it - the VSV stays energized all the time with IGN ON or ACC except when the EGR valve opens for exhaust gas (valve opens because the VSV becomes de-energized by ECM shorting the ground, otherwise circuit stays CLOSED, so VSV will not pass the vacuum signal to the valve on the other side, instead the vacuum is vented to atmosphere).

also make sure the nearby harness grounds are tight and clean. closest one which is being used by i think all sensors reporting to the ECM is located on the back of engine.
5s-fe has it on back of intake manifold (gen4)
1mz-fe gen4 has it on the RH surge tank (i think 2 of them on either side). if this (or maybe others too) ground is bad then EGR VSV circuit may work either intermittently or not at all. either one might cause the egr error codes depending on the details.

if all fails, then there is finally the last thing to check. it's been said that Japanese vacuum modulators tend to fail with lack or excessive back pressure. mind their bottom port which connects to bottom side of the valve (talking about 5s-fe design).
so, if e.g. cat converter is garbage and clogs the exhaust then the excessive back pressure will definitely screw up the vacuum signal passed from the throttle body ports through the modulator.

[fenixus]

ah, and some help from experienced pros too
http://www.motor.com/magazine/pdfs/092009_04.pdf

very good reading, explains a lot