P0402 - Learn from my mistake (1 Viewer)

[Steve7]

This could be a long one.

My CEL came on shortly after purchasing my rig last spring. We were in the middle of moving, so I just lived with the annoying light until this fall.

I started researching on MUD and came to the conclusion that most folks get rid of the code by replacing the EGR modulator. Did I mention that this is also the easiest part of the EGR system to replace, maybe w/ the exception of the EGR Temp Sensor? I contacted CDan and received the part in a few days. The light was off for about a week, and came back on.

I still had not ordered my FSM, so it was back to the "search" function. After reading many threads, it appeared that the next culprit must be the VSV valve. I also concluded that replacing the VSV valve was something that I really didn't want to do myself. I took the truck into the local dealer and asked them to double check the code and tell me what they thought. They confirmed that it was a P0402 code. The technician wanted to isolate the problem so they blocked the tubing from the EGR valve to VSV with a BB. This was the second time that I had heard of this method (first time was here on MUD). Well, the CEL came back on.

Now I'm a little concerned so I go ahead and order the FSM. I read through the EGR section, and still end up thinking that I don't want to mess with changing the VSV. I was a little intimidated by the steps to remove the valve for replacement/testing.

So, I find a Toyota specialist here in Southern MD and explain to them what I've done. They checked the truck out and said that they normally replace the VSV, EGR valve, EGR Mod, and Temp Sensor to correct an EGR malfunction. I scratched my head and told them that the reason that I brought the truck to a specialist is so that I wouldn't waste anymore money swapping parts...I could have done that. I asked them to start w/ the VSV...light comes back on.

I take it back to them, and ask if they had checked the vacuum lines etc... YES.

I give in and tell them to replace the EGR valve as I had already cleaned the Temp Sensor per the FSM and MUD. Guess what? Light comes back on.

I take it back and they replace the Temp Sensor, and clean everything up again for me. Guess what? Light comes back on!

I take it back and they check it out again and told me that there was a loose. I pick up the truck for the xxxth time, and the light came back on yesterday before I got out of the parking lot at home.

I went back to the shop and was as polite as I could possibly be. They explained the troubleshooting process as they saw it, and I explained my version of isolation and tracking down the problem to a specific component. I left with the diagnosis that I needed a new ECM.

So, this morning I'm bound and determined to fix the darn thing myself. I got the FSM back out and reread the theory of operation and then crawled back into the engine compartment.

Guess what I found in the first 15 minutes? The tube that runs through the intake between the EGR valve and the VSV was TOTALLY blocked. It was tough getting the hoses off to check, but I definitely have flow now.

If I understand correctly the VSV will shut off the EGR at a given time based on ....... If this vacuum line is clogged...... the EGR will not shut off, and could result in an excess flow error code.

I'm off now to test drive the truck and run the logic test. I'm not sure if it will cure the problem, but I can at least tell you not to start swapping parts without first checking the simple stuff.

Let me test it and I'll get back to you. Thanks again for all of the awesome input here on MUD...next time maybe I'll pay closer attention to the details.

 

[RavenTai]

If I understand correctly the VSV will shut off the EGR at a given time based on ....... If this vacuum line is clogged...... the EGR will not shut off, and could result in an excess flow error code.

Yep. If the ECU sees any flow during warm up it will throw the 402 after the second drive cycle.

If that does not clear it check the metal tube that passes though the intake. it often pluggs, you can check for clearance all the way through to the throttle body by warming up the engine (to open the vsv) and hook up a vac pump to that line.

If that still does not do it give this a read, a vac gauge will let you troubleshoot it as you drive and should zero in on your problem.

https://forum.ih8mud.com/showpost.php?p=1535318&postcount=10

There is not much on 80 that that a typical DIY mechanic cannot do, the VSV can be done in about an hour with little trouble it is easier to change than it looks, just need 12mm socket some long extensions and a 12mm wrench.

I am sure there are good mechanics out there somewhere that I would trust to work on my my 80, but I have not yet to met one.

 

[tabascoloco]

P0402 code ONLY if cold here!

I found tons of information on the P0401 code but not much on P0402 (excessive flow). I have the new EGR Modulator and the only code my cruiser ever throws is 402. It will ONLY give this code if under load/driving while cold. If I let my engine warm for a few minutes, the CEL WON'T come on. It will only come on if cold and not warmed up at all. I'm unsure about taking off my intake, simply because I had a $4000 engine transplant less than 10k ago!
Therefore, I assume my VSV is bad or EGR is dirty/sticking....

 

[RavenTai]

why would you take off the intake?

 

[smokethedog]

"Guess what I found in the first 15 minutes? The tube that runs through the intake between the EGR valve and the VSV was TOTALLY blocked. It was tough getting the hoses off to check, but I definitely have flow now."

I've been plagued with the 402 for a quite a while now as well. I checked the metal tube that you reference above, and it appears mine is blocked as well. I tried to stick a pipe cleaner through it but it hung up, then I tried running a 1.5mm alan wrench through it and it gets stuck as well, guessing about 1.5" down. Is this tube straight or is there a bend in it? I didnt want to force it and end up breaking something.

How did you clean yours out?
tia

 

[Darwood]

"Guess what I found in the first 15 minutes? The tube that runs through the intake between the EGR valve and the VSV was TOTALLY blocked. It was tough getting the hoses off to check, but I definitely have flow now."

I've been plagued with the 402 for a quite a while now as well. I checked the metal tube that you reference above, and it appears mine is blocked as well. I tried to stick a pipe cleaner through it but it hung up, then I tried running a 1.5mm alan wrench through it and it gets stuck as well, guessing about 1.5" down. Is this tube straight or is there a bend in it? I didnt want to force it and end up breaking something.

How did you clean yours out?
tia

The tube is straight but it connects to another vacuum line on the other end. If you didn't unplug this line and check it out all you are doing is compacting the carbon into the vacuum line. I used a bent paper clip to clean mine out. I also had to clean out the carbon from the vacuum line that runs from the bottom of the tube to the VSV.

If I remember correctly the tube is about an inch long. Just long enough to go through the intake plenum.

 

[Steve7]

Darwood is correct, the tube is ~ 1.5" long.
I was able to get a pair of long nose pliers in to remove the vacuum tube from the VSV. Then I used some safety wire to get through the build up initially. After that I doubled up the wire and twisted it. I ran it through the hole enough to open it up real good, and then blew through it several times to get the junk out of it.
Finally, I reconnected the hose to the EGR, tube, and VSV.

I've had at least 6 cold starts w/o the light coming back on.

Note: I thought about using a drill bit (w/ my fingers)after I had already finished the job.

Good luck!

 

[RavenTai]

Then I used some safety wire to get through the build up initially. After that I doubled up the wire and twisted it.

A&P?

 

[alia176]

Here's a picture of the VSV valve and the surrounding area.

Cheers!

ps

Yes, I'll be changing mine out before the intake manifold goes back on! I don't have any 402 code yet but why take a chance!

 

[tabascoloco]

Hmmm...good idea...

Darwood is correct, the tube is ~ 1.5" long.
I was able to get a pair of long nose pliers in to remove the vacuum tube from the VSV. Then I used some safety wire to get through the build up initially. After that I doubled up the wire and twisted it. I ran it through the hole enough to open it up real good, and then blew through it several times to get the junk out of it.
Finally, I reconnected the hose to the EGR, tube, and VSV.

I've had at least 6 cold starts w/o the light coming back on.

Think I'll try FIRST...if the P0402 comes back, I'll be ordering a VSV and pulling the intake off...thanx

 

[tabascoloco]

why would you take off the intake?

Well, if the code keeps coming back, the most likely solution is to replace the VSV. The intake is super simple to take off, and the bonus is that you get to clean it up really good and gain EASY access to the VSV, PHH, etc. at the same time.

 

[RavenTai]

The VSV is easier than it looks, theaft bolt can be gotton from the bottom with a long extension, the foreward with just a 12mm open end wrench, much easier than removing the intake, if you want to take off the intake anyway well then fair enough.

 

[smokethedog]

I got the metal tube cleaned out. I used a 2.5" 15 ga. finishing nail and a small hammer. Tapped on the nail till it finally broke through. Reamed it through the hole a few times till it moved with relative ease, then blewit out with air. Hope this solves my 402!
thanks for posting this,
smokethedog

 

[panamalexus]

Removal

Hi,

I can see that this is quite a problem with the 80´s and have a question. Can the whole system be removed. I live in Panama so 3 problems: etrem heat, no mechanics that I can trust, no parts except from the US they just Toyota just tried to charge me $500 for a new set of ignition leads and $70 for a fule filter!!

Also EGR and cats are not a requirment here.

Thanks

 

[Shahram]

Does anyone have a photo of the offending hose?

 

[RavenTai]

If you look at the picture in post 9 it is the line coming out of the VSV heading to the left of the screen to the intake, that is the bottom half, at the end of that hose is a small diameter metal tube that passes through the intake to the top side where it tuns into vacuum hose again and heads to the EGR valve, for a pic of the top side look at the first picture in the thread linked in post #2. it is the hose with "#0" in white along its side.

 

[Shahram]

Thanks...so I've located the hose, and where it passes through the underside of the intake. The metal tube that should contain the carbon is the area that passes through the intake? I just want to be sure about this before I go reaming out the wrong thing.

Thanks again.

 

[RavenTai]

yes That is where carbon is sometimes found, not found on all trucks not sure why. on my 80 it was the VSV valve, no carbon was found anywhere in the vac system except for a small amount in the modulator.

 

[Shahram]

Cool. Thanks for the info.

 

[tabascoloco]

What's the blue one called?

What is the blue unit to the right of the VSV called? Is is a check valve?