Camry EGR Valve, Code P0401
in [Toyota]
|
Prev: meow
Next: Gentle art of Aging... (from another group)
From: Ray O on 29 Mar 2010 12:46 "Jeff Strickland" <crwlrjeff(a)yahoo.com> wrote in message news:hoqke9$oea$1(a)news.eternal-september.org... > > "Ray O" <rokigawa(a)NOSPAMtristarassociates.com> wrote in message > news:hopg75$a9r$1(a)news.eternal-september.org... >> >> "Jeff Strickland" <crwlrjeff(a)yahoo.com> wrote in message >> news:hoomij$jl$1(a)news.eternal-september.org... >>> >>> "Ray O" <rokigawa(a)NOSPAMtristarassociates.com> wrote in message >>> news:hooi44$hi9$1(a)news.eternal-september.org... >>>> >>>> "Jeff Strickland" <crwlrjeff(a)yahoo.com> wrote in message >>>> news:hoo2t3$ln6$1(a)news.eternal-september.org... >>>>> >>>>> "Ray O" <rokigawa(a)NOSPAMtristarassociates.com> wrote in message >>>>> news:homlot$me2$1(a)news.eternal-september.org... >>>>>> >>>>>> "Jeff Strickland" <crwlrjeff(a)yahoo.com> wrote in message >>>>>> news:holl8b$k4k$1(a)news.eternal-september.org... >>>>>>> >>>>>>> "Hachiroku ????" <Trueno(a)e86.GTS> wrote in message >>>>>>> news:holh7v$6jn$1(a)news.eternal-september.org... >>>>>>>> On Sat, 27 Mar 2010 09:21:42 -0700, Jeff Strickland wrote: >>>>>>>> >>>>>>>>> I have a friend with a Camry (an '01, give or take a year), that >>>>>>>>> has two >>>>>>>>> codes stored that are both P0401. I'm not sure how the same code >>>>>>>>> can be >>>>>>>> >>>>>>>> >>>>>>>> Common Problems that Trigger the P0401 code: >>>>>>>> >>>>>>>> * Restriction in the EGR passages, usually caused by carbon >>>>>>>> buildup >>>>>>>> * Lack of proper vacuum or electrical signal to the EGR valve >>>>>>>> * Lack of proper EGR system feedback to the computer from the: >>>>>>>> Manifold Absolute Pressure Sensor (MAP) >>>>>>>> Differential EGR Pressure Feedback Sensor (DPFE) >>>>>>>> EGR Valve Position Sensor (EVP) >>>>>>>> EGR Temperature Sensor >>>>>>>> * The EGR Valve is defective >>>>>>>> >>>>>>>> Then, start here: >>>>>>>> >>>>>>>> http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=EC&P=12 >>>>>>>> >>>>>>>> >>>>>>>> A P401 can point to other things: bad vacuum flow; this happened on >>>>>>>> my >>>>>>>> Tercel. Toyota tested the EGR (gratis) and said it was OK. I >>>>>>>> rectified the >>>>>>>> issue by putting a switch on the ECM battery wire. Hit the switch, >>>>>>>> clear >>>>>>>> the memory, drive the car two driving cycles and repeat. >>>>>>>> >>>>>>>> Finally tracked the problem to a clogged vacuum line. At first we >>>>>>>> thought >>>>>>>> it was the vacuum sensor (after the EGR) and then found the hose to >>>>>>>> the >>>>>>>> sensor was clogged. >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>> >>>>>>> I thought the EGR gets dirty and sticks. How do you clean it? >>>>>>> >>>>>>> I'm discounting, for now, electrical or vacuum issues ONLY because >>>>>>> if the problem is a random occurance, this would seem to indicate a >>>>>>> stich valve, not missing signals or bad vac supply. Electrics or vac >>>>>>> issues would be less random and more constant. What I don't know at >>>>>>> this moment is if the problem IS random or not, and that would make >>>>>>> a difference, I think. But I want to start with cleaning the EGR, >>>>>>> but I don't know what cleaner to use, or if the valve can be cleaned >>>>>>> in place or has to come off to be cleaned. >>>>>>> >>>>>> >>>>>> You are way overthinking the problem. I would check the electrical >>>>>> stuff first since it is easy to check and doesn't involve removal of >>>>>> the EGR valve. >>>>>> >>>>>> When you diagnose a problem, check the stuff that is easy to check >>>>>> first, then move to the more complicated stuff, in the order of >>>>>> likelihood. >>>>>> >>>>>> The EGR valve and tube can become clogged with carbon. After you >>>>>> remove the valve, dig out what you can with an awl or screwdriver, >>>>>> being careful not to damage the valve seat. Some solvent may loosen >>>>>> some of the deposits but make sure the solvent is dry before >>>>>> reinstalling the valve. >>>>>> -- >>>>>> >>>>> >>>>> I thought that cleaning it WAS doing the easy stuff first. >>>>> >>>> >>>> The gaskets on the EGR valve should be replaced when the valve is >>>> removed, so just removing it means buying some parts, and messing with >>>> the exhaust system tends to provide ample opportunities for stripped >>>> fasteners so my preference is to put a meter on an electrical component >>>> with the component in place when possible. >>>> >>>> You can also check EGR operation with the engine idling, which is >>>> pretty easy. Provide vacuum directly to the EGR valve with a vacuum >>>> pump or bridged directly from the manifold without passing through >>>> VSV's, and if the EGR valve is opening, the engine should start to idle >>>> poorly and start to stall. If that happens, the EGR valve is not >>>> clogged. >>>> >>>> There are 2 ways to monitor EGR system operation, monitoring EGR >>>> exhaust gas temperature with a sensor and monitoring EGR position with >>>> a sensor. Rather than try to look up all the different permutations of >>>> engine and model year, it would be easier to just know engine and model >>>> year before starting research as you need that info anyway. IIRC, the >>>> 2002 is a different generation than the 2001. >>>> -- >>>> >>> >>> That's the kind of thing I needed to know. Thanks. >>> >>> I was thinking the problem was one those transient kinds of things, and >>> would not happen again very soon. If I'm wrong, then I will be looking >>> at this car in the not too distant future. The woman said the light had >>> been on for a long time -- many months. She assumed that it needed an O2 >>> Sensor but lacks the money to buy one or to visit a mechanic. Since the >>> car runs fine, she ignored the light. >>> >>> If the EGR needs service, then I'll be looking closely at it, this is >>> just a starting place. I knew there was a test on the vacuum side, I >>> just did not know what it was. >>> >> >> My experience with Toyota on-board diagnostics is "transient" problems >> that illuminate the MIL are pretty much non-existent, especially with >> DTC's with 2 trip detection logic. The 2-trip detection logic means that >> transient problems will not illuminate the MIL, and if the problem should >> somehow clear itself up, the MIL will go out. When a MIL is illuminated, >> all clearing the codes does is extend the diagnosis time because it will >> probably turn itself back on. >> -- >> > > > There's only one code, so if there's trouble, it should be back pretty > soon. > > How come the same code can be stored twice? > > I had code 01/02 and 02/02 that were both the same code. My logic says > that the computer would see that it already holds the code that it's > getting ready to report, so it ought not store it again. Clearly my > thinking is flawed because the same code was stored twice. > > I have not run across an instance where the same code is stored twice. Some code readers display pending codes for DTC's with 2 trip detection logic, and IIRC, P0401 is one of the codes with 2 trip detection logic so the reader may be showing the 2 trips. -- Ray O (correct punctuation to reply)
From: aarcuda69062 on 29 Mar 2010 23:39
In article <hoo3un$q35$1(a)news.eternal-september.org>, "Jeff Strickland" <crwlrjeff(a)yahoo.com> wrote: > Sorry, it's the four cylinder. <snip> > I'm not sure of the year, but I know that it isn't older than a 2000 or > newer than a 2002, and my confidence that it's a 2001 is at about 90%. > Unless this particular year is one that strattles model changes, I can take > a generalized answer as nothing more than that. I'm just hoping to get my > arms around the theory right now. Theory; when the EGR is commanded open, the PCM uses the MAP sensor to measure the expected increase in intake manifold pressure. When the EGR is commanded closed, the PCM uses the MAP sensor to measure the expected decrease in intake manifold pressure. If the expected pressure changes do not occur, the P0401 is set. > Cleaning an EGR isn't really dependent on the year of the car. The theory of > what they do and how they do it does not change very much in a year or two. > I'm smart enough to figure this out by removing the damn thing entirely and > going at it. But if this one can be cleaned in place, that helps me a > little. It doesn't need to be removed to see whether it's working correctly. Just use the bi-directional control on your scan tool to command the EGR open and closed. The problem may not be apparent right away, intermittents in any of the VSVs are common and may take upwards of a dozen or more activations before they duplicate. > PS > My cheesey little scan tool helped me fix my BMW that was throwing codes. > Turns out the car has a physical failure of the Smog Pump and the MAF was > bad. The Fuel Trim and Fuel Control (two ways of saying the same thing) came > as a result of the MAF. So it wasn't the O2 sensors as you originally thought... > The O2 Sensors also had issues that came from the paid mechanic that put > them in poorly and damaged the threads on the sensors. I replaced them > because they don't cost all that much on this application. Sounds like you shotgunned 'em anyway. Boogered threads do not cause fuel trim problems. > So, I did take the car to a different mechanic to diagnose the MAF, but he > didn't do anything with his $1200 scanner that I couldn't do with my $120 > scanner. Can't say for sure whether that was the result of him not utilizing the tool to its full capability or merely that MAF problems are so basic that it really shouldn't take more than two soup cans and a string to figure them out... > He did use his scanner to reprogram my car's computer because it > was running around with an old set of firmware loaded. A $1200 BMW flash capable scan tool? Ain't no such animal. Hell, a generic J2534 pass thru box is minimum $1400.00 and that is without the interface cable. > He also flushed my > transmission, which is a job that I did not want to do. Why not, all you really need to do is open your wallet and start throwing $20 bills into the wind. Kudos to him, he charged you the stupid tax and has you believing you got something of value for it. > Bottom line, > I do pretty well. You had outside help, anyone can see that. > Thanks for asking. I didn't, but that has never stopped you from blowing your own horn. |