Re: 1998 Explorer V8 Displaying code P1131
On Tue, 23 Aug 2005 05:46:05 GMT, "ross n via CarKB.com" <forum@CarKB.com>
>>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.
>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
>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
>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.
The only reason some people get lost in thought
is because it's unfamiliar territory.