Nate

Two weeks ago my Explorer displayed the code that bank 1 oxygen sensor
was slow to respond (I forget the code #). I replaced the bank 1
sensor and disconnected the battery which reset the codes and forced
the vehicle to relearn. Vehicle ran without throwing any code until I
was entering a freeway at high acceleration. It now reads the codes
PO401 (EGR Isufficient flow detected) and P1131 Lack of HO2S11
Switch-Sensor indicates Lean. I read that the vehicle is in open loop
until the sensor reaches 600 degrees F and at WOT (wide open throttle).
Entering the freeway I did not have the pedal to the floor but was
trying to get up to 60mph from a stop. One note also is that I
replaced the EGR valve about 10,000 miles ago.

Any thoughts?

ross n via CarKB.com

Nate wrote:
>Two weeks ago my Explorer displayed the code that bank 1 oxygen sensor
>was slow to respond (I forget the code #). I replaced the bank 1
>sensor and disconnected the battery which reset the codes and forced
>the vehicle to relearn. Vehicle ran without throwing any code until I
>was entering a freeway at high acceleration. It now reads the codes
>PO401 (EGR Isufficient flow detected) and P1131 Lack of HO2S11
>Switch-Sensor indicates Lean. I read that the vehicle is in open loop
>until the sensor reaches 600 degrees F and at WOT (wide open throttle).
> Entering the freeway I did not have the pedal to the floor but was
>trying to get up to 60mph from a stop. One note also is that I
>replaced the EGR valve about 10,000 miles ago.
>
>Any thoughts?

Insufficient EGR is most often a bad DPFE sensor. The DPFE monitors the EGR
valve to be sure it is working correctly, and sends a voltage from 1 volt at
idle to 5 volts at maximum EGR to the computer, which then decides, based on
the voltage, if the EGR is Ok. So the DPFE simply tattles on the EGR valve.
However, when the DPFE fails, it does not send enough volts to the compuer.
Computer then thinks "that dam* EGR is not doing what I told it to" and sets
the insufficient EGR code,when in fact EGR valve is just fine. Its the DPFE
that is fibbing. This is more likely in your case because of the newer EGR
valve.

Nevertheless, you should probably do some checking before just swapping out
the DPFE. They are about 80 bucks, and I suggest NAPA for the part. There
are two small special high temperature hoses you will see below your EGR
valve down by the exhaust manifold that run back to the DPFE sensor on the
back of the intake manifold. Make sure they are connected. Some times they
burn thru, and they can do lots of damage quickly if they fall off. Clean
them out if you do the DPFE sensor. Different sizes, and the right
connections matter.

Also, pull a vacuum on your EGR valve, make sure it holds it. With the
engine running at idle, pull a vacuum on it, and it sould almost kill or will
kill the engine.

There is an EGR solenoid under the upper intake manifold, and the EVR valve.
Solenoid opens vacuum from the intake to the EGR system when computer tells
it to, and the EVR actually applies vacuum to the EGR valve when the computer
tells it to. They could be bad, but they are not common problems.

Fix EGR first, then go after the other code.

Alan Moorman@visi.com

On Tue, 23 Aug 2005 05:46:05 GMT, "ross n via CarKB.com" <forum@CarKB.com>
wrote:

>Nate wrote:
>>Two weeks ago my Explorer displayed the code that bank 1 oxygen sensor
>>was slow to respond (I forget the code #). I replaced the bank 1
>>sensor and disconnected the battery which reset the codes and forced
>>the vehicle to relearn. Vehicle ran without throwing any code until I
>>was entering a freeway at high acceleration. It now reads the codes
>>PO401 (EGR Isufficient flow detected) and P1131 Lack of HO2S11
>>Switch-Sensor indicates Lean. I read that the vehicle is in open loop
>>until the sensor reaches 600 degrees F and at WOT (wide open throttle).
>> Entering the freeway I did not have the pedal to the floor but was
>>trying to get up to 60mph from a stop. One note also is that I
>>replaced the EGR valve about 10,000 miles ago.
>>
>>Any thoughts?
>
>Insufficient EGR is most often a bad DPFE sensor.


What does DPFE mean?


>The DPFE monitors the EGR
>valve to be sure it is working correctly, and sends a voltage from 1 volt at
>idle to 5 volts at maximum EGR to the computer, which then decides, based on
>the voltage, if the EGR is Ok. So the DPFE simply tattles on the EGR valve.
>However, when the DPFE fails, it does not send enough volts to the compuer.
>Computer then thinks "that dam* EGR is not doing what I told it to" and sets
>the insufficient EGR code,when in fact EGR valve is just fine. Its the DPFE
>that is fibbing. This is more likely in your case because of the newer EGR
>valve.
>
>Nevertheless, you should probably do some checking before just swapping out
>the DPFE. They are about 80 bucks, and I suggest NAPA for the part. There
>are two small special high temperature hoses you will see below your EGR
>valve down by the exhaust manifold that run back to the DPFE sensor on the
>back of the intake manifold. Make sure they are connected. Some times they
>burn thru, and they can do lots of damage quickly if they fall off. Clean
>them out if you do the DPFE sensor. Different sizes, and the right
>connections matter.
>
>Also, pull a vacuum on your EGR valve, make sure it holds it. With the
>engine running at idle, pull a vacuum on it, and it sould almost kill or will
>kill the engine.
>
>There is an EGR solenoid under the upper intake manifold, and the EVR valve.
>Solenoid opens vacuum from the intake to the EGR system when computer tells
>it to, and the EVR actually applies vacuum to the EGR valve when the computer
>tells it to. They could be bad, but they are not common problems.
>
>Fix EGR first, then go after the other code.


Alan Moorman

The only reason some people get lost in thought
is because it's unfamiliar territory.

Paul Fix

=================================

ross via CarKB.com

Differential pressure feedback EGR. Hit you search engine. You'll get lots
of reading.


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