First and Second Day of Ownership - P0401

[togles]

Well, the honeymoon was short lived from purchasing this thing Friday afternoon The previous owner cleared the P0401 so I got it on my ride home. So I dug in Saturday afternoon and started researching, was up until 4:30am today watching 50-60of EGR and EVAP system videos and reading tons of forum posts and talking to AI. I had no prior experience with troubleshooting or even a good understanding of EVAP and EGR systems, but after all the research last night, I woke up at 7:30 and felt confident enough to tear into this and have been working on it for 12 hours today.

Results -
EGR is good. I am able to open and close the diaphragm with a vacuum tool so I am good there.
I have a bad EGR Vacum Modulator, totally clogged up, deteriorated. On order.
I also have a bad VSV, its essentially stuck.
VSV Observations/Learning -
It measures 35.4 ohms, so electrically speaking its good, however, its clogged up and malfunctioning as it is stuck closed and will not release vacuum / open when 12v is disconnected.
The VSV is open(ie flowing freely) with no voltage applied. When applying 12v, it clicks and at that point it closes the valve, allowing for vacuum pressure to build. In my case, the VSV that I removed from the truck was initially open when I first started messing with bench testing it, air flowing freely. I applied 12v to it and was able to pull solid vacuums with 12 volts applied on both ports of the VSV, and when removing the voltage, the vacuum would drop immediately. So initially I was thinking I was good with the VSV. However, after the 2nd or 3rd time, when removing the voltage, vacuum remained, it was just stuck at that point. I bench tested the Doorman 911-850 that someone else mentioned using and that operated very much the same way, as my initial tests on the stock one, but its was working 100% of the time. I would have stuck with it but the plug from the ECU harness VSV wont plug into this Doorman part so I returned it and am going to get it from Toyota I think.

Other than that, I am definitely relocating my new VSV when I get it to outside of the intake manifold, trying to work on that in the future with it mounted under the intake manifold is for the birds.

Ill try to keep this thread updated as I go along and complete this job.

Below is my VSV Bench test setup.

Here are some pics of the VSV after unbolting from the underside of the intake manifold.

 

[togles]

Here is a pic of the vacuum port on the underside / back part of the intake manifold. Just above this on the outside of the intake manifold would be the vacuum port that the EGR valve is connected to. These are connected. From under the manifold, the vacuum hose would connect to the VSV valve, the drivers side port for lack of a better reference.

 

[george_tlc]

Good debugging. Yep, the VSV can become intermittent, working for a bunch of time and then getting stuck. So, code comes, goes away, comes back. Eventually it just gets stuck and the code will continue to return even after clearing with a scanner.

I replaced mine years ago (probably close to 10), the factory ones last many years, I've replaced only once in my 29 or so years of ownership and have a spare sitting for the next time around. At that stage, removing the intake manifold (which is reasonably easy) is worthwhile if for no other reason than to replace the spaghetti of vacuum lines under there Toyota sells cut lengths of the vacuum line and you then just cut to fit.

cheers,
george.

 

[george_tlc]

And you only remove the top 'half' of the intake manifold, so other than some long extensions to reach some of the bolts that are only accessible from below, it's an easy job. To be 'factory correct', just have a new metal gasket on hand ready for replacement, ditto for the throttle body to upper intake metal gasket.

cheers,
george.

 

[togles]

And you only remove the top 'half' of the intake manifold, so other than some long extensions to reach some of the bolts that are only accessible from below, it's an easy job. To be 'factory correct', just have a new metal gasket on hand ready for replacement, ditto for the throttle body to upper intake metal gasket.

cheers,
george.

Thanks, yeah i have to call Toyota tomorrow to try and get the egr and throttle body gaskets, as well as the vacuum modulator and vsv and about 30 feet of this vacuum line lol.

 

[Brindleboxer]

IIRC I ordered 90999-92004 for the vacuum line. This is the smaller diameter but there are a couple larger hoses that can be ordered separately.