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egr code 401 on Rav4 Insufficient Low EGR Flow


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jackpruitt
Novice

Sep 5, 2016, 4:24 PM

Post #1 of 17 (1038 views)
egr code 401 on Rav4 Insufficient Low EGR Flow Sign In

I got a 401 code on a 1998 Rav4 2.0 ltr. how I determine what I need to fix. I guess it could be
the EGR. egr modulator, vacuum lines, vse or a clogged intake passage that the egr buckles up to. How should I go about
determining what is causing the code?


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Sep 5, 2016, 4:29 PM

Post #2 of 17 (1037 views)
Re: egr code 401 on Rav4 Insufficient Low EGR Flow Sign In

T in a vacuum gauge between the transducer and the EGR valve to see if there is even vacuum getting to the EGR valve while your driving. You may need to clear the trouble code to get the system working. Then take a vacuum pump and apply vacuum to the valve to see if it stalls the engine at idle.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Sep 5, 2016, 4:31 PM)


jackx
User

Sep 5, 2016, 5:44 PM

Post #3 of 17 (1028 views)
Re: egr code 401 on Rav4 Insufficient Low EGR Flow Sign In

Thanks, I will do that

If I want a mechanic to fix this problem how do I go about
and select one who is qualified to fix it.

I do know this can be caused by the vse not allowing any vacuum to get to the
egr and I do know that you need to put vacuum as you say to the egr to see if it
opens and stalls the car. If it does not do that then the egr is bad or there is
carbon built up in the intake where the egr bolts on.

The mechanic I took it to said he was going to pull the intake off it and
clean out the egr passage. He did not even look at it.
I believe you have to drill out 4 plugs and clean out the intake that way.
I don't think you have to put the intake.

How do I know if this guy knows what he is doing.
My big question is how do I know who to take it to. I know the dealer can
fix it but surely there are mechanic out there that can fix it too cheaper.


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Sep 5, 2016, 5:58 PM

Post #4 of 17 (1026 views)
Re: egr code 401 on Rav4 Insufficient Low EGR Flow Sign In

Run your tests first and see what you find out.

I'd be apprehensive to take it to someone who stated they would have to remove the intake to clean out the passages without even diagnosing the problem first.
Ask your friends, neighbors, or relatives where they take their vehicles for repair. Maybe you can get some good referrals.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


jackx
User

Sep 6, 2016, 11:57 AM

Post #5 of 17 (1009 views)
Re: egr code 401 on Rav4 Insufficient Low EGR Flow Sign In

Well I did three tests

first I hooked up a hand vacuum pump to the vacuum line going into the top of the egr. I started the
car and when I pumped it the motor sputtered and died. So I guess that means the egr is working and
it is not plugged up with carbon in the intake

second I hooked the hand vacuum pump to the one nipple on the left side of the vacuum modulator valve
and had the motor revved up to 3000 and the meter read 20 pounds. So I guess the modulator is ok.

Third I pulled the to vacuum lines off the front of the throttle body that go to the vacuum modulator valve
The front nipple coming out of the throttle body must be blocked because it had no vacuum. That line
goes to the front nipple on the modulator valve.
The rear nipple coming out of the throttle body is hooked to the hose that goes to the modulator valve rear
right hand side nipple which is directly across from the rear left hand side nipple. That side has only one nipple
and it goes down to the vacuum solenoid switch. Anyway that nipple on the throttle body had plenty of vacuum.

I decided to put a y in the rear nipple on the throttle body that has vacuum and ran hoses from that y to both
nipples on the vacuum modulator valve.

I know I need to remove the throttle body and clean it but I did not have time today. My stepson needs the
truck to go to work.

I still think the vacuum solenoid swith may be bad but it is a pain getting to and I don't have time. If it throws a
401 code I will take it to a mechanic. I had it at the mechanic's shop and he said that the solenoid switch probably
is not bad and he thinks the modulator switch is bad even though it passed the test. He agreed that the egr valve
appears to be ok. He did not tell me to put the y connector in but I did it because I am betting that both nipples
should be getting a vacuum from the throttle body.

If I have to because it still throws a code I will take it back to the shop and have him clean up the throttle body
so both throttle body nipples have a vacuum and it that does not fix it I will have him check out the vacuum solenoid
switch. I know there are vacuum test you can do on them to see if they are ok. The problem now is I don't have
time to remove. It. It is down on the backside of the motor and you have to jack it up and pull the wheel off to
get to it. Plus the local autozone does not carry it.

You got any ideas as to how to nail down why it is throwing the p0401 code? Hopefully I am headed in the right
direction


(This post was edited by jackx on Sep 6, 2016, 11:59 AM)


kev2
Veteran
kev2 profile image

Sep 6, 2016, 2:22 PM

Post #6 of 17 (1000 views)
Re: egr code 401 on Rav4 Insufficient Low EGR Flow Sign In

there are tutorials on line google


https://www.youtube.com/...401+1998+Toyota+Rav4


jackx
User

Sep 6, 2016, 4:01 PM

Post #7 of 17 (993 views)
Re: egr code 401 on Rav4 Insufficient Low EGR Flow Sign In

thanks for your help. I did find a diagram of the vacuum flow to a toyota
egr modullator valve and it does indicate that the front vacuum port on the
throttle body would not have vaciuum until the butterfly is opened up
past the port. I will take off the Y connector and put the vacuum lines
back the way toyota designed them to fit. Then I will cross my fingers
the p0401 does not come back. So far my step son has driven it 20 miles
to work and no code so far. As soon as it has 2 systems not ready I will
run iI through inspection. In Texas a vehicle this old can pass with 2
systems not ready.


(This post was edited by jackx on Sep 6, 2016, 4:02 PM)


jackx
User

Sep 7, 2016, 8:01 AM

Post #8 of 17 (983 views)
Re: egr code 401 on Rav4 Insufficient Low EGR Flow Sign In

checked it this morning and it had a 401 code pending, so I ordered
a vsv switch, giess mechankic was wrong about the modulator valve
being bad


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Sep 8, 2016, 11:11 AM

Post #9 of 17 (959 views)
Re: egr code 401 on Rav4 Insufficient Low EGR Flow Sign In

Did you end up not having vacuum to the EGR valve on your gauge when you test drove the vehicle?

You can test the VSV using your hand held vacuum pump and a 12 volt test light. Did you make sure that you have exhaust gas flow from the tube that connects to the back pressure transducer when you rev the engine?





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


jackx
User

Sep 8, 2016, 1:35 PM

Post #10 of 17 (948 views)
Re: egr code 401 on Rav4 Insufficient Low EGR Flow Sign In

I only used a hand help vacuum pump with a guage so I did not
check it during a test drive. I did test the egr valve by pumping
the vacuum pump with it connected to the egr and it did cause
the motor to die.

I will get the new vsv switch tomorrow but I won't have access
to the truck til next week. After I get the switch off I may test
it.

The only test I did to the modulator was I hooked the vaccum pump
up to the Q nipple and it jumps to about 20 on the vacuum guage
when you rev the motor to 3000 rpm. I assuimed it was ok. I put
a nw modulator valve on it anyway because the mechanic said
I should. So it should be ok. I know by the test that the vacuum does
get to the vsv switch and the egr does work when gets vacuum gets
to it so the switch must be bad.


jackx
User

Sep 15, 2016, 8:51 AM

Post #11 of 17 (912 views)
Re: egr code 401 on Rav4 Insufficient Low EGR Flow Sign In

Well I tried but saw no way to get the vsv off because this Rav4 is a
4wd. Now I figure it was time to call in the A team.

I called the Toyota house and they wanted $375 but before I took
it to them I took it by a Vietnamese mechanic I a;ways try to use because
I can trust him to not overcharge me. He said he would do it for $60
bucks.

He got her done but raised the price to $90 bucks because it was
a 4wd. I checked the old vsv by connecting 12 volts to the electical
connection and the switch appears to be dead. So, hopefully this will
eliminate the p0401 egr code.


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Sep 15, 2016, 1:48 PM

Post #12 of 17 (902 views)
Re: egr code 401 on Rav4 Insufficient Low EGR Flow Sign In

Appears that you probably solved the issue. What is the resistance reading of the solenoid coil? Some of those solenoid are pretty quiet when you energize them.

Let us know how it turns out.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


jackx
User

Sep 15, 2016, 2:32 PM

Post #13 of 17 (896 views)
Re: egr code 401 on Rav4 Insufficient Low EGR Flow Sign In

I could not get any reading at ohm test range at 200 or
any other range other than 2000k and then it was 440. I
suspect since it appears it should be tested at 200 and
should show at least 36 it must be shorted. I'm in way over
my head now so you need to get back to me and tell
me what this means


(This post was edited by jackx on Sep 15, 2016, 3:18 PM)


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Sep 15, 2016, 4:50 PM

Post #14 of 17 (887 views)
Re: egr code 401 on Rav4 Insufficient Low EGR Flow Sign In

I agree, the resistance of the solenoid should be around 35 ohms. Do you mean 2K ohms? 2000K would be 2,000,000 ohms or 2M ohms. 440 ohms would be too much resistance in that solenoid for sure. Shorted windings would cause the resistance to be less than 35 ohms.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


jackx
User

Sep 15, 2016, 5:42 PM

Post #15 of 17 (884 views)
Re: egr code 401 on Rav4 Insufficient Low EGR Flow Sign In

2,000,000 or 2000k which my cen-tech multimeter calls it.
I use the 200 range to test battery cables too

Thanks again for taking time to help me. The link to the
tutorials was very helpful. Your help is always the best
I get anywhere else.


(This post was edited by jackx on Sep 15, 2016, 5:49 PM)


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Sep 15, 2016, 5:53 PM

Post #16 of 17 (881 views)
Re: egr code 401 on Rav4 Insufficient Low EGR Flow Sign In

There is a better way to test battery cables than using an ohm meter to test them. Ohm meters have there place at times, but you really want to test the cables when they have starter current running through them. That's a whole other story for a different topic though.

You think you would see 400 ohms on the 2000 ohm setting...hmmm. Maybe it is 400M ohms...which is basically an open circuit. Either way the VSV is junk.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


jackx
User

Sep 16, 2016, 4:35 AM

Post #17 of 17 (874 views)
Re: egr code 401 on Rav4 Insufficient Low EGR Flow Sign In

Its fixed. this morning the egr system shows it is ready.






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