99 Toyota Camry v4 Code P0401

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

jon11 - 17 Oct 2007 02:38 GMT

Hi Guys,
Check light came on couple days back. Error Code Reads P0401 EGR Flow
Insufficient. Some body was telling if we replace the Air Filter it will
go away. I haven't changed the airfilter from last 5 months. Can you guys
give me some advice on this, Appreciate your help
Thx

--
Message posted using http://www.talkaboutautos.com/group/alt.autos.toyota.camry/
More information at http://www.talkaboutautos.com/faq.html

Reply to this Message

Nobody Important - 17 Oct 2007 03:32 GMT

> Hi Guys,
> Check light came on couple days back. Error Code Reads P0401 EGR Flow
> Insufficient. Some body was telling if we replace the Air Filter it will
> go away. I haven't changed the airfilter from last 5 months. Can you guys
> give me some advice on this, Appreciate your help

It's probably not your air filter, but have a look at it anyway and
replace it if it's dirty.

Try looking at the Emission Control manual on camrymanuals.com (yours is
a Gen 4 Camry). There will be a diagnostic procedure in there.

Sometimes all it takes is to clean the EGR valve.

There are quite a few threads about P0401 in the Gen 3&4 forum on
toyotanation.com.

Reply to this Message

Diwa - 17 Oct 2007 14:59 GMT

This problem (P4001) started in my car (2000 camry) two weeks back.

It seems like there are 5-6 reasons for this:
1) EGR valve bad (Do vacuum test at idle to verify this)
2) EGR vacuum modulator bad (Block port P and R and blow air thru port
Q)
3) VSV (for EGR) bad. Difficult to locate this. Have to get under car
for this.
4) Hoses or port clogged (In EGR valev or vacuum modulator or throttle
body inlets)
5) Temp sensor bad (This is what the OBD uses to detect whether EGR
operated after command to open it)
And a couple of others reasons.

Reply to this Message

Diwa - 22 Oct 2007 14:47 GMT

> > Hi Guys,
> > Check light came on couple days back. Error Code Reads P0401 EGR Flow
[quoted text clipped - 12 lines]
> 5) Temp sensor bad (This is what the OBD uses to detect whether EGR operated after command to open it)
> And a couple of others reasons.

An update.

I cleaned the 3 vacuum hose from EGR Vacuum modulator and 1 hose from
EGR valve amd also the ports leading to throttle body
Used a thin metal wire first and then compressed air.

And now check engine light (for P0401) no longer appears.

And to think of, the local mechanic wanted to replace the EGR valve
(for $200 parts included).
Somewhere, I had read that that is what most mechanics do for P0401.
They take the easiest path of first replacing the EGR valve.

Reply to this Message

johngdole@hotmail.com - 27 Oct 2007 05:05 GMT

Diwa is right.

Check the EGR valve first by using a free loaner MityVac vacuum pump
on the EGR valve itself. If the engine runs rough at idle when you
pull vacuum then you know the valve is good.

Most of the problems come from carbon-plugged small vacuum ports/
hoses. Cleaning them should make things work most of the time. (This
includes the small ports in the throttle body that send vacuum signals
to the vacuum modulator)

> Hi Guys,
> Check light came on couple days back. Error Code Reads P0401 EGR Flow
[quoted text clipped - 6 lines]
> Message posted usinghttp://www.talkaboutautos.com/group/alt.autos.toyota.camry/
> More information athttp://www.talkaboutautos.com/faq.html

Reply to this Message

johngdole@hotmail.com - 27 Oct 2007 05:13 GMT

Reply to this Message