I am working on a 2010 with less than 100k miles. Recently, I changed the plugs and meticulously cleaned the EGR system and put it all back together. Now I have the P0401 and have not been able to delete it. I replaced the valve and step motor with a used one, but still have the code. Long story short, I have tried to adjust the magnetic coil inside the valve body and I have been able to find tighten the coil and put it all back together but I keep getting the permanent/pending code. I have tried the drive pattern to a T with no luck either. Is there an update on the ECU that I need to install? I have TS but I do not have the TIS version. Yes, I cleaned the manifold as well. Any help would be appreciated!
That code is for: “EGR insufficient flow”. Check to see if you have an EGR disconnected after you cleaned the system. Check the connector
I just realized that you mentioned that a perminent code is still set, which would indicate that you need to complete a drive cycle in order for it to clear. I’m not sure what criteria the drive cycle requires, but usually it will clear itself, given a few normal trips. At most it would clear after about 100 miles. Give it a try.
I already tried the drive pattern, to no avail! I keep getting a "pending" code so it won't help to do the drive pattern to eliminate the permanent code. I had cleaned the EGR and the engine runs great! Everything is bolted down tight. I just can't figure out why I am still getting the "pending" code when I take if for a mile of so drive. Just really tricky... Anyone?
The drive cycle criteria is much more than a 1 mile drive. It’s a little more complicated than that. Like I said, I don’t know the exact requirement but I’m sure it can be looked up on Google.
I have the info on the Drive pattern.... HOWEVER, there is no sense doing the drive pattern if I cannot drive for one mile without getting a pending code: P0401. There is a problem SOMEWHERE in the EGR that I cannot figure out and I was hoping someone could shed some light on this nagging issue without throwing $$$ at it in the form of a new EGR valve or whatever. Actually, I already tried a used ( supposedly good) EGR valve on it and I get the same code. Anyone? Thank YOU in advance!
Is there a software update that I need to do? Does anyone know about this? I am at a loss here and that is AFTER performing the drive pattern and getting a NORMAL! What the actual heck? Can anyone help me out here??? Thank YOU!
Have you tried just testing it out some? Start the engine, idle it, use the active tests in Techstream to move the valve position upward step by step, watch the manifold pressure reading. On mine I'll generally see the pressure start to increase around 10 steps open or so, and by step 14 or so the idle gets pretty rough. Some people with more clogged systems have reported having to open the valve more like 20 or 30 steps before the idle gets shaggy. At least that would give you some idea what is or isn't happening.
Yes, Sir Chapman I did try the active test on the step motor. And yes, it did move from 4 psi to about 7 or 8 when i got into the 20th step or so... So I guess that is OK? I am not sure what the reading SHOULD look like but I am still scratching my head! Thank YOU for your input! I have a new/used MAP sensor to try out new week too.
Well, that doesn't sound like anything is obviously b0rked. Pressure goes up when you tell the valve to open, goes back down when you close it. Seems by amounts not too different from mine. Not much to be going wrong, it would seem. Did you have a passenger/designated Techstream watcher in the car with you while you were driving the confirmation pattern, to make sure the Data List really did show "Idle Fuel Cut" for at least 5 seconds in step 11 of the pattern? Did you query the "All Readiness" DTC judgment (step 20)? What was it? I trust you are explicitly clearing the codes as step 3 of driving the confirmation pattern?
I drove the pattern for a minimum of 5 minutes and then stopped the car and read the DTC judgement: first couple of times it said INCOMPLETE and then finally it said NORMAL. Then, not 15 seconds later, I looked at the screen and it said "pending" on the P0401 code. That was B4 having the chance to finish the pattern. So that time, I did not get to the fuel cut. No, I did not have a co-pilot... Then I tried the pattern again and got ABNORMAL. I don't know how to follow the instructions more closely than I have been and I do understand that I must complete the drive pattern to erase the "permanent" DTC. I must have driven the pattern 10 times in the last week or so and always got varying results. Maybe I need to do the first leg of it for 8 minutes? I don't know. I don't have any hair left. My understanding is that once the pattern has a NORMAL judgement, then the "permanent" DTC just drops off by itself immediately. BTW, the car drives fine... I replaced the valve and step motor, I removed and replaced and cleaned the intake manifold... The only thing I have not looked into that are considered problem areas is the MAP sensor and the engine ECU. Thank you sir Chapman! What next???
Well, it doesn't really smell like an ECU problem to me ... the ECU seems to be doing too many things right, including showing you MAP readings that change when you expect them to, and seem to be in the right ballpark. You could try comparing the MAP sensor reading to another pressure gauge you trust, or swap with another sensor and compare the readings. It doesn't seem out of the ballpark though. If I did swap them, I would want to actually compare their readings, maybe while blocking the manifold passages and applying some known levels of vacuum, rather than just going for another drive to see what happened. That way I'd be more sure that it really was or wasn't something to do with the sensor. Every now and then I run into a puzzler that does result in some hair tugged out. This sounds like you've got one. The answer usually makes total sense, once you're looking back on it.
https://www.google.com/url?sa=t&source=web&cd=&ved=2ahUKEwjc3dPu-4TtAhWeGTQIHdIMDmMQFjABegQICRAF&url=https%3A%2F%2Fwww.torquenews.com%2F8113%2Ftoyota-prius-p0401-egr-insufficient-flow-solved%2Famp&usg=AOvVaw2UNIReyvs_U3elrixPcsTN This is definetly worth the read. Keep an open mind even if you think you have covered everything. Used parts can throw you a curve ball
Thanks BZzap! Peter Neilson has been helping me with the problem for over a month now.... obviously, we have not been successful! Not even a tuft left.
I went out and tested the '10 again today. I did not use the active test. I just cleaned the MAP and MAF and put it back together and watched. I just watched the MAP values as I stepped on the gas. From a value of 14 psi when the engine is off and all the way to 4 PSI when the engine is revving over 2 G's. Does this mean my MAP sensor is headed in the wrong direction? Anyone? I thought the MAP should show MORE PSI when the air flow through the intake is higher...? Thank YOU!
This behaviour is correct and matches my 2010. The engine pulls a vacuum relative to atmospheric pressure.
