Ok I just bought an 01 S2000 that used to have a turbo kit on it. The originally engine blew so the motor I have has only 200 miles on it (I bought the car with the new engine). The CEL is on for P0411. Here is what the Honda dealership has founb so far. They originally thought it was the air pump so that was completely replaced. Took it home on a Fri. CEL back on first thing Sat. morning so I cleared the code again. The CEL did NOT come back on all day until the first start on Sun. So I took the car back this past Tuesday. They noticed a vacuum leak in one of the hoses that are on the top center of the motor. They thought that would have fixed it but it did not. So then they noticed that the ECU wiring was messed with because of the turbo timer and fuel management system that was on the car so they fixed all of the wires and then put in a new ECU and that still did not fix it. Keep in mind the CEL does not always come on in every start. I recently read that people found that they messed up the check valve hose arrangement and that this is what was the fix for their cars. I did not hear Honda say anything about the check valve hoses which I will also tell them about tomorrow. Is there anything else that could be causing this issue? Please let me know. Thanks

 

The first step in this diagnosis should have been to check all vacuum lines, their connections for cracked hoses and the white check valve alignment (it may be backwards). Go to this thread and follow it step by step, then reset the ECU with the other link below. If the CEL comes back on, then procede with the next phase of your detective work.
https://www.s2ki.com/forums/index.php?showtopic=105368

http://forums.s2ki.com/forums/index.php?showtopic=183490

 

thanks xviper. Yeah I already read those articles and it is the exact symptoms I am experiencing. I printed everything out and took them to the dealer. Unfortunately the mechanic that has been assigned and working on my car has a long weekend and will not be back until tuesday so I have to wait to see if this fixes it. The service manager said that the vacuum lines was the next thing he was going to try but also said that he looked at them before and they seemed correct. That doesn't mean the solenoids/check valve are flowing the right way though. I plan on going to the shop tomorrow to (try) to look at the vacuum lines. He kept the air box out so should the lines be easy to see now? If this doesn't fix it then God help me. He has also been talking with the Honda Tech line that they deal with and they seem to think it is something with the vacuum lines. I have owned the car for 2 weeks and only have been able to drive it for 2 days! I want my car back.

 

"Seemed" is the operative word here. I've been getting a couple of PMs lately on this very subject. One owner indicated the same thing. The mechanic said everything was in order. Upon closer inspection, the one way check valve was installed BACKWARDS! Techs tend to overlook simple things because it is beneath them to even consider the simple stuff with adequate determination. I'm not saying that yours is backwards, but certainly don't have them take for granted that all the connections and hoses are in good condition. A cracked hose at a connection is invisible till you take the thing in your hand and manipulate it. If I were a busy, well paid tech and it wasn't my car, I sure wouldn't bother going to the time & trouble to be that discriminating on such a minute detail.

 

Well I do agree that the wiring harnesses had to be repaired because there were wires that were cut and not going anywhere anymore. They did not replace the whole harness they just sodered everything back to the way it should be. Also right now they are only charging me for the wire fix (2hrs) and no diagnostic time because my car is still under the Honda Care warranty that covers everything. They can't claim the wires to Honda Care because it is obvious that they were tampered with and I agreed. The guy I bought the car from took off the turbo before he took it in when he blew the motor and Honda Care covered it even with the strong opinions from the tech that a turbo or sc was on the car. So I still have a warranty and a car with 200 mile motor. The tech did admit that once this problem is fixed I really have a great car so for that I am greatful. The main problem was that the guy I bought the car from would never come clean to Honda on what he actually did to the car. That is why it is taking them a long time to diagnose it because with not knowing what was done to the ECU or anything else, they had to look at everything that would cause that code to pop up. I am glad they did because they found other things that needed to be replaced. It is just the fact that I haven't been able to really enjoy the car but since I really do not have to pay much for this I would rather they get everything right instead of bringing it in every week. Thanks for your help. I will post next week on the results.

 

Yep, track it down one thing at a time. First, the vacuum lines and if that doesn't do it, then retrace all the wiring. Who knows how much stuff was altered with that turbo and subsequent re-wiring.
Good luck.

 

xviper,

guess what. I went back to the dealer to get something I left in the trunk. Luckily they left the hood up so I went to take a look at the check valve. There it was the OPPOSITE direction! So I tell the service advisor that this was wrong and I would like them to flip it around, put the stock air box on and I can take it home finally because this was most likely it. He wouldn't let me because he needs to get approval from the Manager(who doesn't work Sat.) to let me take the car. I could not believe this. There tech has been working on this for almost 2 weeks and I go in for 1 minute and I probably found the problem but now I have to wait until Monday.

 

After working on it for 2 weeks, I'm sure they're going to tell you that check valve was "only" one of MANY things wrong with the car. You know what they say about "PRIDE", right. Check again to see if they actually corrected the check valve direction. Good luck.

 

I have one more question. Since the CEL only comes on during cold starts would I be correct to say that the reason for that is because the check vale is only used in warm up mode? Meaning once the engine is warm that part of the system is cut off so that is why I can clear the code after warm up and not throw it until the next day when it is cold again or anytime during a day when it has been sitting for awhile? I just want to know more about the function of that part so when I talk to them I can sound more knowledgeable than just saying oh that's wrong. Thanks

 

Yep, the secondary air injection system, of which that check valve is a part of only functions after a start. If your engine is stone cold, it'll run for a few minutes. If the engine is already warmed up or hot, it may come on but immediately shut off as soon as it senses the engine temp.
It pumps air into the exhaust manifold during engine warm up in an effort to reduce emissions.