P0402 - Learn from my mistake

[LCHardriver_02]

94SRUNNER - I was thinking that because the tube was clogged, it may have been covering up an actual low flow problem, since it did not have a reference. I am planning on systematically checking the system as time allows, starting with the modulator.

Kernal - You are correct. Reading this thread helped me understand what the line did and why others were getting the 0402 code. I thought I would check mine just to see if it was plugged and it was. I was able to push a small straightened out paper clip, followed by a larger one that just fit the tube. After this my 0401 code showed up.

alia176 - I will do a search for that thread, as I have a hard time getting a few fingers in the area around the VSV! If I an move it to a better location, boy howdy I will, plus understanding this system seems paramount to being able to fix it properly!

Thanks guys!

 

[LCHardriver_02]

Was this the only point in the EGR you messed with?

Sorry, I forgot to answer this question. The answer is no. I also replaced vacuum hoses with new. This was the only thing I did otherwise. I could check by placing the old hoses back on, as I kept them all and see if that changes anything. Thoughts on whether new hoses would cause an issue? I believe I got the all back on correctly, as I worked one hose at a time.

 

[94SRUNNER]

I don't think the new hoses would have caused this. One other thing that I did that helped while eliminating P0402 was to pull the EGR temp sensor and clean the sensor tip with a brass brush. It was caked with a think layer of carbon. Cleaned it off and the code went away. Not saying this was the only thing that did it, but I believe it was a factor as it was one part of my EGR system cleaning effort.

 

[LCHardriver_02]

Good to know. I will take a look at that too. Thanks much!

 

[alia176]

Good to know. I will take a look at that too. Thanks much!

You have a good attitude, I think you'll figure it out. The hardest part is to understand what is happening and the cure might be as simple as a vac hose with split ends! If you study the vacuum diagram under the hood, you'll have a good understanding of what is happening.

VSVs are simple on/off devices. Either they work with 12vdc or they don't. The temp sensor is another simple device - resistance changes as the tip gets hotter. The EGR modulator is a giant valve that works with vacuum signals. Apply a vac (mouth suction will work) and the valve moves.

Yup that's it - you now know everything

 

[LCHardriver_02]

Thanks much alia. The nice thing about my 80 is that other than this code and a few small oil leaks, the bugger runs like a top! So, I do not feel impatient with getting to the bottom of this, although, as my son and I were discussion yesterday, I do not like having a CEL present at any time. That said, the hoses with split ends were the reason for me wanting to start by just replacing all of those, although there were a few under the air chamber that I just could NOT reach! I am planning on getting those replaced as soon as I can either get a pair of really long needle nose pliers in there to pull the old hoses off and push the new ones back on, and I want to just step through the FSM check out and sequentially eliminate all of the components, as being the problem child / children. I truly think this system still has the '95 components, so it would not surprise me if I had multiple components failing. One thing at a time and slowly but surely, I think I will get it.

As for staring at the diagram on the hood, yep... got a bit of a crick in my neck doing so this weekend! I was also staring at the two diagrams in the FSM, making sure I knew where all of the hoses were located, as some where very hard to find!

 

[alia176]

Thanks much alia. The nice thing about my 80 is that other than this code and a few small oil leaks, the bugger runs like a top! So, I do not feel impatient with getting to the bottom of this, although, as my son and I were discussion yesterday, I do not like having a CEL present at any time. That said, the hoses with split ends were the reason for me wanting to start by just replacing all of those, although there were a few under the air chamber that I just could NOT reach! I am planning on getting those replaced as soon as I can either get a pair of really long needle nose pliers in there to pull the old hoses off and push the new ones back on, and I want to just step through the FSM check out and sequentially eliminate all of the components, as being the problem child / children. I truly think this system still has the '95 components, so it would not surprise me if I had multiple components failing. One thing at a time and slowly but surely, I think I will get it.

As for staring at the diagram on the hood, yep... got a bit of a crick in my neck doing so this weekend! I was also staring at the two diagrams in the FSM, making sure I knew where all of the hoses were located, as some where very hard to find!

I agree, you may have original parts under there. Interesting thing about the hoses, I've tried purchasing 3/16" and 1/8" hoses from NAPA but they don't really as well as the metric hoses from Toyota. I ended up replacing them all to Toy hoses eventually. Just a FYI.

 

[LCHardriver_02]

Did you find that you had leaks with the 3/16" and 1/8" hoses, as this is what I ended up using because they did not have metric at our local O'Reilly's auto parts store?

 

[alia176]

Did you find that you had leaks with the 3/16" and 1/8" hoses, as this is what I ended up using because they did not have metric at our local O'Reilly's auto parts store?

They just didn't fit "snugly", for a lack of a better word! The metric hoses are tight on those nipples.

 

[LCHardriver_02]

yeah, I did notice this too. There is nothing like having your nipples clamped correctly!

 

[alia176]

yeah, I did notice this too. There is nothing like having your nipples clamped correctly!

as I keep telling my wife "honey, deep down, we're all 12 years old"....

 

[LCHardriver_02]

ROFL!! Sorry, I could not resist! OK, seriously, can you buy the metric tubing in bulk somewhere?

 

[alia176]

You can buy bulk hoses from Toyota but they may exist in NAPA type places too.

He said "nipple" - beaviss and butthead

 

[LCHardriver_02]

I will try my local dealer, as the O'Reilly's down the street does not carry metric.

 

[dmnddave]

I'd like to add to this thread...

About 4 years ago and like others before, I changed the pricey EGR and Vac Modulator which made my code disappear for about two weeks just long enough to get past smog check. Of course when it came back, I ignored it until the last smog check 2 years ago. I believe I just had Autozone reset my code, head straight over to the check station and had it pass that way. Fast forward two more years and its time for smog check again, still the P0402 code is there. I forgot all about Registration and Smog two months ago, my tags are expired and I'm reminded via a late notice letter... time to hustle. I was hoping to get LT's MAF upgrade in through this next round of smog check (after I fix my code of course) but got pulled over by the Man and was forced to get this resolved quickly (can't wait, what a shame). This past Saturday I decided to take the throttle body off and poke around to try and find the infamous clogged tube.

I found it and yep, it was clogged... to help others know exactly what this is, I took some pics just to help with understanding this issue. btw, don't be fooled by the little hole in the carbon build up... I took the pic AFTER I tried reaming it with a drill bit... no paper clip was gonna pentrate this crap - its was hard and took a lot of effort to drill through it. Actually went 1-3/4" deep and still didn't break through... had to hand ream using the drill bit from the bottom (engine side) upwards another 1/8" to break through. No more codes.

Hope this helps!

WET

Alright first post. I just had an 80 shipped to STL from Pompano Beach FL unseen on an ebay purchase. I get the truck and its sweet. Driving home from work that night the CEL light comes after 10 miles or so. Here we go. I take it to an indy mechanic and he determines i need a temp sensor due to 401 and comments that almost all hoses and vacuum lines are new. I tell him to go ahead and replace it. I pick the truck up and its back-CEL. This guy it too far from my work so i bite the bullet and take it to the local dealer. They tell me the modulator is bad so we go ahead and replace that. 2 cold starts and what comes next 402. Take it back and they say the VSV must be bad so we replace that. What do you know-402 again. So I bear down on this site and tell these guys to clean this 1.5" tube found on post#22 and ........FIXED! The dealer thanks me for figuring this out! ih8mud saved my ass on this one. What a great resource. After reading all this goodness on these codes I could have easily replaced that temp sensor and modulator myself. Not sure about VSV (not sure if i even needed a new one). Anyway, the seller and two mechanics tried to fix this and MUD had the answer! Right on boys.

 

[PDoyle]

So your hooked now like the rest of us!

 

[alia176]

Alright first post. I just had an 80 shipped to STL from Pompano Beach FL unseen on an ebay purchase. I get the truck and its sweet. Driving home from work that night the CEL light comes after 10 miles or so. Here we go. I take it to an indy mechanic and he determines i need a temp sensor due to 401 and comments that almost all hoses and vacuum lines are new. I tell him to go ahead and replace it. I pick the truck up and its back-CEL. This guy it too far from my work so i bite the bullet and take it to the local dealer. They tell me the modulator is bad so we go ahead and replace that. 2 cold starts and what comes next 402. Take it back and they say the VSV must be bad so we replace that. What do you know-402 again. So I bear down on this site and tell these guys to clean this 1.5" tube found on post#22 and ........FIXED! The dealer thanks me for figuring this out! ih8mud saved my ass on this one. What a great resource. After reading all this goodness on these codes I could have easily replaced that temp sensor and modulator myself. Not sure about VSV (not sure if i even needed a new one). Anyway, the seller and two mechanics tried to fix this and MUD had the answer! Right on boys.

Congrats and welcome to the madness <-- official mud salute.

Also, you just figured out that the Indies and Dealers are mostly monkeys who lost the art of diagnosing problems. However, they excel at swapping out parts and bill you for it.j

I strongly urge you to read our FAQs that were painstakingly put together by mods and several contributors. We won't be quizzing you on them but it's good for you to know how to access info efficiently for future.

 

[uscmas412]

My new to me 80 is throwing a P0402. I inspected the tube going through the intake and sure enough, it was blocked. I've determined I'll need to remove the throttle body to properly inspect the other side. Before I do, I want to make sure I've located the correct hose. The following picture is from another member's 80 with the TB removed. I've highlighted the hose in a red circle:

 

[Herd Bull]

I created an account because I need to thank you guys. I had the 402 code and was not sure where to start. After reading the forum here, I checked the line that passes through the intake that connects the hoses for the vsv to the EGR valve. It was plugged with carbon / debris. I used a small drill bit for a combination of finger drilling and lightly tapping with a hammer to unclog the line. Thanks a lot for the info on this guys!!

HERD BULL

 

[ZRTALPHA1]

Another thing to add to this is that if you so choose, you can simply by pass this nipple and run the hose from point A to point B w/o going through this nipple. You see, this nipple is simply a passage through the intake, it doesn't actually open up inside the intake.

See the picture below and you'll see the other side of the intake where the nipple comes out. It's directly to the left of the red circled VSV.

I literally thought the same, I bypassed the hose but the check engine light is still on does it take a while to go off or should i just reset it