P0401 is a 2-trip logic meaning you could have a stored code. I would reset the ECM by pulling the EFI fuse and be sure you are starting from a known point.
-B-
Yet another dreaded 401 thread....(few diag questions)
- Thread starter 98 SNAKE EATER
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P0401 is a 2-trip logic meaning you could have a stored code. I would reset the ECM by pulling the EFI fuse and be sure you are starting from a known point.
-B-
Does disconnecting and reconnecting the battery cables have the same effect ?
Yes.
-B-
-B-
- Thread starter
- #44
Yeah, I scanned her before leaving the shop and the 401 was still there, so I cleared it...
Finger crossed
- Thread starter
- #45
BTW, thanx Beuwulf for filling us in on removing the VSV without pulling the intake 
If it wasn't for you and a few others, I would've went by the book and ordered up a complete gasket set
If it wasn't for you and a few others, I would've went by the book and ordered up a complete gasket set
You're welcome. It's Beowulf.
-B-
Coming soon to a theater near you
Not So Good News
Going by the FSM, my old VSV checks out ok
Rick
mine checked out Ok out of the truck per the FSM also, but in the truck it was intermittent, seamed to work for a wile during warm up and shortly after but after a heat soak it would fail,
snake eater,OK, the new VSV showed up at my shop this morning (PN#90910-12079)
It's definitely normally open as I can blow air through it
Don't have the time to install it today, but I did manage to shoot a short video of how I tested the EGR valve and the VSV hoses for leaks
YouTube - 1FZ-FE EGR Valve Testing
Note: when the VSV hoses are pinched, the EGR valve holds vacuum just fine and since it stalls the engine instantly, I've pretty much ruled it out as a problem...
Rick
I am in the process of diagnosing my egr system. I have done the test as you have on you youtube video.
When I apply vacuum, the engine stumbles slightly.
When I apply vacuum with either of the vsv hoses pinched the engine stumbles more and ALMOST dies. I'm was sucking hard-I am a non smoker.
I have not pulled and cleaned the egr valve yet, should that be next?
- Thread starter
- #50
If you pinch the hoses and it holds vacuum, then the EGR Valve's diaphragm good
That's exactly how mine worked out
On a sidenote, I she hasn't thrown a code since I replaced the VSV
So, although the engine does not die, would you say the egr valve is not the issue?
- Thread starter
- #52
If it still holds vacuum and the engine stumbles to the point of almost dying, the valve should be good...
If it doesn't hold vacuum, check the hoses...
If the hoses are good and it still doesn't hold vacuum when to pinch them, then the EGR valve's diaphragm might be torn (replace)
I think this is a good time for me to add some status on this. The CEL came back after 1700 for me. I thought I could get away with the original VSV but I was wrong. That got me motivated to replace the VSV with the brand new one that I had gotten from Dan months ago. While doing that, I also replaced all the hoses. One of the ('U' shaped) hoses (I forget which port it is) was so hardened that it had broken into pieces. I compared the original VSV with the new one; air flow was significantly different between the two. I want to see how the inside of the original VSV looks like. One of these days I'm going to split it open with my grinder. Anyway, so far I've got more than 7K miles on the beast and my CEL and code 401 have been off.
Obviously this particular CEL has been a bugger for us all. Yet there's no concrete solution available, as far as I know. IMHO, I say we eliminate this useless appendage from our engines and come up with a way to trick the ECU. Onur (Beno) just needs to come with an EGR eliminator kit (at production level) and may be a hack to the ECU to keep the CEL off (for those of us who have to go through inspection).
Obviously this particular CEL has been a bugger for us all. Yet there's no concrete solution available, as far as I know. IMHO, I say we eliminate this useless appendage from our engines and come up with a way to trick the ECU. Onur (Beno) just needs to come with an EGR eliminator kit (at production level) and may be a hack to the ECU to keep the CEL off (for those of us who have to go through inspection).
not sure if this will be of any use, but this is what I found. i also had a MIL. Had a shop pull the code (no scanner yet) and it was the 401.
Anyway, I could pull the EFI fuse and the MIL would be off for maybe a full day, but always appeared on day 2. Maybe the two trip thing?
Anyway, went to trouble shoot the simple stuff that I could per the FSM.
Diconnected the temperature sensor to see resistance and noticed that there was some corosion on the male spades the sensor connects to. Used an eraser to clean the spade and added a little dielectric grease and so far no MIL. Can not guarantee this is a longterm solution, but I have my fingers crossed.
Anyway, I could pull the EFI fuse and the MIL would be off for maybe a full day, but always appeared on day 2. Maybe the two trip thing?
Anyway, went to trouble shoot the simple stuff that I could per the FSM.
Diconnected the temperature sensor to see resistance and noticed that there was some corosion on the male spades the sensor connects to. Used an eraser to clean the spade and added a little dielectric grease and so far no MIL. Can not guarantee this is a longterm solution, but I have my fingers crossed.
Obviously this particular CEL has been a bugger for us all. Yet there's no concrete solution available, as far as I know. IMHO, I say we eliminate this useless appendage from our engines and come up with a way to trick the ECU. Onur (Beno) just needs to come with an EGR eliminator kit (at production level) and may be a hack to the ECU to keep the CEL off (for those of us who have to go through inspection).
IIRC, Gary Coberly has already figured out a way to correctly trick the computer into thinking everything is fine with the EGR valve. I have yet to find the post with this information in it.
That said, since taking off the EGR valve and putting in blocking plates w/ OEM gaskets, I have not had a P0401 code at all. I do have O2 sensor codes (P0125/P0141) but no codes at all to do with the EGR system.
My VSV is blocked from the intake side to the charcoal canister. The temp sensor is still plugged in as well. All vacuum hoses are basically plugged back into the intake manifold so all the vacuum lines go back into each other.
The truck runs fine (except beyond the full rich due to O2 sensor) and am very happy with the deletion of the EGR.
-o-
I'd be interested to know if you get the P0401 code after you have resolved all your 02 sensor related (and others if any) codes.
Man I am already day dreaming about having no EGR crap in my Engine bay! It's a good feeling baby! Although I don't have the CEL for it, I could use that extra space for some thing else
Man I am already day dreaming about having no EGR crap in my Engine bay! It's a good feeling baby! Although I don't have the CEL for it, I could use that extra space for some thing else
Yeah, me too Riad. I am going to get the O2 sensor related stuff taken care of first and see what happens. My guess, nothing.
-o-
- Thread starter
- #58
A little update:
It's been well over a year without throwing a code, but last week, while driving down from NYC to Orlando, I got an MIL again
Drove it for a few days without issue (my scanner was at the shop and I didn't have access to it), but when I finally scanned her, I got the dreaded 401
Cleared the code and it came back within 15 minutes of driving, so it was definitely a hard fault
EGR valve checked out fine
Did the suck test and it held vacuum with the engine off
Did a running test and it stalled right away
Pulled the modulator filter, but it was sopping wet
I made the mistake of trying to blow it dry with some compressed air and it just fell apart
Luckily, there's a scrap Camry behind the shop and the filter looked band new, so I swiped it
Wiped away some moisture that was in the modulator, installed the Camry filter, cleared the code and the light remained off for about 200 miles
Same code popped up, checked the filter and it was sopping wet again
This time I squeezed it dry, then removed the modulator completely and blew it out with some air cause it had quite a bit of moisture in it...
Re-installed it, did a blow test and it checked out fine...
Did a running blow test and I felt a bit more resistance @ 2500 RPM's, but I wasn't sure if it was adequate
Cleared the code and it came back after another 200 miles of driving
Same code popped up, pulled the filter and it was dry
Yanked the modulator out of both the Cruiser and the old Camry to compare....
They look identical with the exception of color and part numbers, but the Camry modulator held vacuum from the bottom port and mine didn't, so I'm guessing the diaphragm on mine is kaput
The testing sequence for the Camry modulator is the same for the Cruiser, except it calls for a 3000 RPM running test (Cruiser is only 2500)
I don't think there's much difference between the two (if any), so I just installed the Camry modulator and the blow test checked out just fine with good resistance when running
That's where I'm at as of now, but I'll report back later (I'll be placing an order for the correct modulator on Monday)
On a sidenote, would a busted diaphragm on a modulator suck up that much moisture
The filter looked like it was sitting in a pool of water when I pulled it out
I figure it probably happened during the snow/ice storm a few weeks ago
It's been well over a year without throwing a code, but last week, while driving down from NYC to Orlando, I got an MIL again
Drove it for a few days without issue (my scanner was at the shop and I didn't have access to it), but when I finally scanned her, I got the dreaded 401
Cleared the code and it came back within 15 minutes of driving, so it was definitely a hard fault
EGR valve checked out fine
Did the suck test and it held vacuum with the engine off
Did a running test and it stalled right away
Pulled the modulator filter, but it was sopping wet
I made the mistake of trying to blow it dry with some compressed air and it just fell apart
Luckily, there's a scrap Camry behind the shop and the filter looked band new, so I swiped it
Wiped away some moisture that was in the modulator, installed the Camry filter, cleared the code and the light remained off for about 200 miles
Same code popped up, checked the filter and it was sopping wet again
This time I squeezed it dry, then removed the modulator completely and blew it out with some air cause it had quite a bit of moisture in it...
Re-installed it, did a blow test and it checked out fine...
Did a running blow test and I felt a bit more resistance @ 2500 RPM's, but I wasn't sure if it was adequate
Cleared the code and it came back after another 200 miles of driving
Same code popped up, pulled the filter and it was dry
Yanked the modulator out of both the Cruiser and the old Camry to compare....
They look identical with the exception of color and part numbers, but the Camry modulator held vacuum from the bottom port and mine didn't, so I'm guessing the diaphragm on mine is kaput
The testing sequence for the Camry modulator is the same for the Cruiser, except it calls for a 3000 RPM running test (Cruiser is only 2500)
I don't think there's much difference between the two (if any), so I just installed the Camry modulator and the blow test checked out just fine with good resistance when running
That's where I'm at as of now, but I'll report back later (I'll be placing an order for the correct modulator on Monday)
On a sidenote, would a busted diaphragm on a modulator suck up that much moisture
The filter looked like it was sitting in a pool of water when I pulled it out
I figure it probably happened during the snow/ice storm a few weeks ago
did the moisture in the filter small like exhaust at all?
the bottom port of the modulator is exhaust pressure, were the diaphragm to get a hole in it then exhaust could get into the upper portion of the modulator, this usually shows up as carbon that people find in the modulator, in the winter I could see it condensing moisture out of the exhaust gases but it would smell like exhaust.
moisture in a vacuum system in the winter will wreck havoc,
my modulator also had a hole in it, hard to see in the pics but there is a pin hole leak
the bottom port of the modulator is exhaust pressure, were the diaphragm to get a hole in it then exhaust could get into the upper portion of the modulator, this usually shows up as carbon that people find in the modulator, in the winter I could see it condensing moisture out of the exhaust gases but it would smell like exhaust.
moisture in a vacuum system in the winter will wreck havoc,
my modulator also had a hole in it, hard to see in the pics but there is a pin hole leak
- Thread starter
- #60
Yep, when I squeezed the filter dry, my hands did smell like exhaust
It was surprisingly clean too (clear as drinking water)
It was surprisingly clean too (clear as drinking water)
