Code 402

I have a 1999 Explorer with 108000 miles. Last week it started pinging
with a very low load. The fuel was low so I filled the tank, got on the
freeway and headed home. As I exited the freeway I noticed the Check
Engine light on. After some reading, I tried to clean the MAF sensor
with liquid freon. I put it together, disconnected the battery,
reattached the battery and powered up the engine. No more check engine
or pinging.
Two days latter the check engine light and ping came back. This time I
disconnected the battery and tried more air and liquid freon on the MAF.
Re attached the battery and no check engine for a few days. Yesterday
the check engine came back. I went to Auto Zone and they said it had
code 402 and I should check it out (not any help). What could it be and
what should I look at?

TIA, Dave
--
Diving is life! The rest is just details.

P0402 = EGR flow detected at idle

There should not be any EGR flow at idle. I don't know how the PCM manages
the engine when it detects this fault. In general, EGR flow reduces the
combustion temperature, allowing ignition timing to advance without pinging,
so there seems to be a connection between pinging and a malfunctioning EGR
system.

The code could be set because there is flow at idle, or because the system
detected flow, even though there isn't any. The list of possible causes for
EGR flow when it should not exist is too long to repeat here. Some a EGR
valve stuck open, stuck EGR regulator solenoid, plugged solenoid vent or
electrical shorts. Indication of flow when there isn't any could be due to
misrouted, plugged, kinked or iced hoses or due to a bad DPFE sensor. If I
had to make a bet instead of systematically troubleshooting, it would be on
the latter, because of the age of the vehicle and the fact that these
sensors are subjected to a harsh environment and don't last forever (mine
failed at about 70000 miles). Nevertheless, I don't think that throwing
parts at any problem is a good idea.
The EGR system is not that complicated, and with the help of a decent manual
and a few basic tools, troubleshooting is not such a big deal. A scanner
will save poking through wires or back-probing, but is not essential. If
this sounds daunting, my advice would be to check the two hoses leading to
the DPFE, and if intact, to leave the rest to the professionals.


"Davenandee" > wrote in message
om...
> I have a 1999 Explorer with 108000 miles. Last week it started pinging
with a very low load.
.....
>I went to Auto Zone and they said it had code 402 and I should check it
out (not any help). What could it be and
> what should I look at?

I'll agree with HT.... One down and dirty way to check for a leaking EGR
valve is to start the motor from cold and feel the EGR valve (do NOT rev the
motor... leave it idle).... If the EGR valve starts getting hot then it is
either being commanded open or it is leaking internally.


"Davenandee" > wrote in message
om...
> I have a 1999 Explorer with 108000 miles. Last week it started pinging
> with a very low load. The fuel was low so I filled the tank, got on the
> freeway and headed home. As I exited the freeway I noticed the Check
> Engine light on. After some reading, I tried to clean the MAF sensor
> with liquid freon. I put it together, disconnected the battery,
> reattached the battery and powered up the engine. No more check engine
> or pinging.
> Two days latter the check engine light and ping came back. This time I
> disconnected the battery and tried more air and liquid freon on the MAF.
> Re attached the battery and no check engine for a few days. Yesterday
> the check engine came back. I went to Auto Zone and they said it had
> code 402 and I should check it out (not any help). What could it be and
> what should I look at?
>
> TIA, Dave
> --
> Diving is life! The rest is just details.
>

By most posts on this newsgroup, the P0402 code generally seems to indicate
a clogged DPFE sensor. Replacement is a relatively simple process. 2
hoses, 2 screws, and the sensor plug. About $50 for the part IIRC. Mine
got clogged up around 105K.
"Davenandee" > wrote in message
om...
>I have a 1999 Explorer with 108000 miles. Last week it started pinging with
>a very low load. The fuel was low so I filled the tank, got on the freeway
>and headed home. As I exited the freeway I noticed the Check Engine light
>on. After some reading, I tried to clean the MAF sensor with liquid freon.
>I put it together, disconnected the battery, reattached the battery and
>powered up the engine. No more check engine or pinging.
> Two days latter the check engine light and ping came back. This time I
> disconnected the battery and tried more air and liquid freon on the MAF.
> Re attached the battery and no check engine for a few days. Yesterday the
> check engine came back. I went to Auto Zone and they said it had code 402
> and I should check it out (not any help). What could it be and what should
> I look at?
>
> TIA, Dave
> --
> Diving is life! The rest is just details.
>

Captain Coleman wrote:

>By most posts on this newsgroup, the P0402 code generally seems to indicate
>a clogged DPFE sensor. Replacement is a relatively simple process. 2
>hoses, 2 screws, and the sensor plug. About $50 for the part IIRC. Mine
>got clogged up around 105K.
>"Davenandee" > wrote in message
. com...
>
>
>>I have a 1999 Explorer with 108000 miles. Last week it started pinging with
>>a very low load. The fuel was low so I filled the tank, got on the freeway
>>and headed home. As I exited the freeway I noticed the Check Engine light
>>on. After some reading, I tried to clean the MAF sensor with liquid freon.
>>I put it together, disconnected the battery, reattached the battery and
>>powered up the engine. No more check engine or pinging.
>>Two days latter the check engine light and ping came back. This time I
>>disconnected the battery and tried more air and liquid freon on the MAF.
>>Re attached the battery and no check engine for a few days. Yesterday the
>>check engine came back. I went to Auto Zone and they said it had code 402
>>and I should check it out (not any help). What could it be and what should
>>I look at?
>>
>>TIA, Dave
>>--
>>Diving is life! The rest is just details.
>>
>>
>>
>
>
>
>
My '01 SportTrak went through this, and I ended up replacing both the
DPFE and the EGR valve.
Now before you start on me throwing parts at the engine, the EGR was so
carboned up that it wouldn't
move. I later cleaned it up with carb cleaner, but never reused it.
With the new EGR, I still got the code,
and then replaced the DPFE. That was an altogether different design,
larger and installed backwards com-
pared to the original. Codes went away, CEL light too.