Re: VSV or EGR problems, Please help

OK, I check a factory service manual, and the possible causes of a P0401
diagnostic trouble code (DTC) are:
1) EGR valve stuck closed - you already checked this so this is probably not
the problem.
2) Open or short in EGR gas temp sensor circuit - we'll come back to this
3) Open in VSV circuit for EGR - you are getting voltage at the VSV so this
is not it.
4) Improper operation of the VSV for EGR - you already check this so this is
probably not the problem.
5) bad vacuum control valve (VCV) - we'll come back to this.
6) vacuum hose disconnected or blocked - hopefully, you already checked
this. Manifold vacuum should be healthy.
7) bad ECM - I've looked at a pretty fair number of cars and have never
personally run across a bad ECM and I pretty much always toss this cause out
the window.

You can never mind what I suggested previously about the EGR position
sensor.

The next step is to check the EGR gas temp sensor. It is located in the
tube between the EGR valve and the intake air chamber. To check, disconnect
the wires from the sensor and measure the resistance between the 2 terminals
on the sensor. Don't do this immediately after driving. Resistance should
be between 2.5 kilo ohms and 600 kilo ohms. If the ohmmeter reads 750 kilo
ohms or more or less than 200 ohms, replace the EGR gas temp sensor.

check the wiring to the EGR gas temp sensor to make sure it is not damaged
or the insulation is nicked.

The VCV for the EGR is located between the intake air chamber and the VSV
for EGR. There is no electrical connection to the VCV. It is a short round
cylinder with 2 vacuum hoses. To check the VCV, unplug the vacuum hoses,
hook up a Mighty Vac to port S and plug port Z with your finger. Pump the
Mighty Vac 3 times so it reads between 8.6 and 11.8 in Hg, stop pumping,
wait 10 seconds, and check the gauge. It should read between 4.4 and 7.1 in
Hg. If not, replace the VCV.

That's about it, if these don't work, I'm out of ideas.

good luck!

--

Ray O
(correct punctuation to reply)

Ray O wrote:[color=blue]
> OK, I check a factory service manual, and the possible causes of a P0401
> diagnostic trouble code (DTC) are:
> 1) EGR valve stuck closed - you already checked this so this is probably not
> the problem.
> 2) Open or short in EGR gas temp sensor circuit - we'll come back to this
> 3) Open in VSV circuit for EGR - you are getting voltage at the VSV so this
> is not it.
> 4) Improper operation of the VSV for EGR - you already check this so this is
> probably not the problem.
> 5) bad vacuum control valve (VCV) - we'll come back to this.
> 6) vacuum hose disconnected or blocked - hopefully, you already checked
> this. Manifold vacuum should be healthy.
> 7) bad ECM - I've looked at a pretty fair number of cars and have never
> personally run across a bad ECM and I pretty much always toss this cause out
> the window.
>
> You can never mind what I suggested previously about the EGR position
> sensor.
>
> The next step is to check the EGR gas temp sensor. It is located in the
> tube between the EGR valve and the intake air chamber. To check, disconnect
> the wires from the sensor and measure the resistance between the 2 terminals
> on the sensor. Don't do this immediately after driving. Resistance should
> be between 2.5 kilo ohms and 600 kilo ohms. If the ohmmeter reads 750 kilo
> ohms or more or less than 200 ohms, replace the EGR gas temp sensor.
>
> check the wiring to the EGR gas temp sensor to make sure it is not damaged
> or the insulation is nicked.
>
> The VCV for the EGR is located between the intake air chamber and the VSV
> for EGR. There is no electrical connection to the VCV. It is a short round
> cylinder with 2 vacuum hoses. To check the VCV, unplug the vacuum hoses,
> hook up a Mighty Vac to port S and plug port Z with your finger. Pump the
> Mighty Vac 3 times so it reads between 8.6 and 11.8 in Hg, stop pumping,
> wait 10 seconds, and check the gauge. It should read between 4.4 and 7.1 in
> Hg. If not, replace the VCV.
>
> That's about it, if these don't work, I'm out of ideas.
>
> good luck!
>
> --
>
> Ray O
> (correct punctuation to reply)[/color]

For the temp sensor I only have the EGR valve and a tube that goes
right to the engine, there isn't a sensor on it. This isn't the map
sensor mounted on the firewall or one right around the air intake is
it.
I am going to borrow a vac pump today and test the VCV first.
Thanks for all your help.

"BigB" <bnovinger@adelphia.net> wrote in message
news:1156427506.057870.246080@75g2000cwc.googlegroups.com...[color=blue]
>
> Ray O wrote:[color=green]
>> OK, I check a factory service manual, and the possible causes of a P0401
>> diagnostic trouble code (DTC) are:
>> 1) EGR valve stuck closed - you already checked this so this is probably
>> not
>> the problem.
>> 2) Open or short in EGR gas temp sensor circuit - we'll come back to this
>> 3) Open in VSV circuit for EGR - you are getting voltage at the VSV so
>> this
>> is not it.
>> 4) Improper operation of the VSV for EGR - you already check this so this
>> is
>> probably not the problem.
>> 5) bad vacuum control valve (VCV) - we'll come back to this.
>> 6) vacuum hose disconnected or blocked - hopefully, you already checked
>> this. Manifold vacuum should be healthy.
>> 7) bad ECM - I've looked at a pretty fair number of cars and have never
>> personally run across a bad ECM and I pretty much always toss this cause
>> out
>> the window.
>>
>> You can never mind what I suggested previously about the EGR position
>> sensor.
>>
>> The next step is to check the EGR gas temp sensor. It is located in the
>> tube between the EGR valve and the intake air chamber. To check,
>> disconnect
>> the wires from the sensor and measure the resistance between the 2
>> terminals
>> on the sensor. Don't do this immediately after driving. Resistance
>> should
>> be between 2.5 kilo ohms and 600 kilo ohms. If the ohmmeter reads 750
>> kilo
>> ohms or more or less than 200 ohms, replace the EGR gas temp sensor.
>>
>> check the wiring to the EGR gas temp sensor to make sure it is not
>> damaged
>> or the insulation is nicked.
>>
>> The VCV for the EGR is located between the intake air chamber and the VSV
>> for EGR. There is no electrical connection to the VCV. It is a short
>> round
>> cylinder with 2 vacuum hoses. To check the VCV, unplug the vacuum hoses,
>> hook up a Mighty Vac to port S and plug port Z with your finger. Pump
>> the
>> Mighty Vac 3 times so it reads between 8.6 and 11.8 in Hg, stop pumping,
>> wait 10 seconds, and check the gauge. It should read between 4.4 and 7.1
>> in
>> Hg. If not, replace the VCV.
>>
>> That's about it, if these don't work, I'm out of ideas.
>>
>> good luck!
>>
>> --
>>
>> Ray O
>> (correct punctuation to reply)[/color]
>
> For the temp sensor I only have the EGR valve and a tube that goes
> right to the engine, there isn't a sensor on it. This isn't the map
> sensor mounted on the firewall or one right around the air intake is
> it.[/color]

No. The system has to have a way of detecting EGR flow, I'm not sure how
that happens on your particular car.
[color=blue]
> I am going to borrow a vac pump today and test the VCV first.
> Thanks for all your help.
>[/color]

I recommend paying for access to techinfo.toyota.com (I think it is $10/day)
for the pdf version of the factory service manual for your particular car.
Check the engine (EG) section in the manual under code P0401. Keep in mind
that the manual often refers to other sections for testing a particular
component like the VCV.

good luck!
--

Ray O
(correct punctuation to reply)