cleared code 0401/drove 40miles??came back on AGAIN..

[mike96]

The code ( 0401)came back after 40 miles (second time).the first couple of times code 1518 came out ,believe i fixed that (no code on that )... MY question is if i reset code 0401 (clear)go to my nc /inspection station no mil light on///will i pass inspection ,or does code reset clear everything needed to read for (odb2) inspection???...so i can get sticker,&fix later ..thanks to whom has the answers ....

 

[naval-avi8or]

The code ( 0401)came back after 40 miles (second time).the first couple of times code 1518 came out ,believe i fixed that (no code on that )... MY question is if i reset code 0401 (clear)go to my nc /inspection station no mil light on///will i pass inspection ,or does code reset clear everything needed to read for (odb2) inspection???...so i can get sticker,&fix later ..thanks to whom has the answers ....

I can almost assure you that your MIL light will come on during that test. You can reset a EGR related DTC and can drive for hundreds of miles with no MIL light but when you slow down and start causing the EGR system to kick in its gonna pop the code again. On these V-8's it's almost always a bad DPFE sensor and you can get one at your local parts store and replace it in a few minutes. V-6 was a little different and a good cleaning of the intake nostriles was usually the problem.

 

[avocadoman1]

in california, i had a similar problem (0401).
when i went to get emissions, with no lights showing, he said that my computer needed to go thru a "full" cycle before he could give me a positive test. he asked me to drive around for a while. and by that time, the light came back on.

"The EGR flow rate test is performed during a steady state when engine speed and load are moderate and EGR Vacuum Regulator duty cycle is high. The monitor compares the actual Differential Pressure Feedback EGR circuit voltage to a desired EGR flow voltage for that state to determine if EGR flow rate is acceptable or insufficient. This is a system type test and may trigger a DTC for any fault causing the EGR system to fail.

The DTC associated with this test is DTC P0401.
P0401 Exhaust Gas Recirculation Flow Insufficient Detected"

we ended up pulling the surge tank and installing another EGR (used) sensor.

i haven't seen the light since.

 

[mike96]

I was told you do not have to take the surge tank off to change the dpfe sensor?,it looks like to me you have to?..Why are people buying that part used??(price point).. The car had been sitting 4 awhile with reg unleaded in it ran it out,, been putting prem unleaded back in her ,that would have not caused P0401 CODE??? Thanks for the WEALTH OF information FROM ALL MEMBERS ,THAT I HAVE BEEN RECEIVING & SEARCHING ON THIS #1 AND ONLY GREAT SITE...

 

[avocadoman1]

I was told you do not have to take the surge tank off to change the dpfe sensor?,it looks like to me you have to?..Why are people buying that part used??(price point).. The car had been sitting 4 awhile with reg unleaded in it ran it out,, been putting prem unleaded back in her ,that would have not caused P0401 CODE???

it's a much easier install by removing surge tank. we have done it so many times now that it's no big deal.
we initially thought that it was a "clog" in the orifice leading to the sensor as that is usually the problem. after a couple of failed cleanings, we opted to try something else.
we had a 60K motor on a totaled 98-SHO in the driveway so in an effort to identify the "real" problem, we decided to try the used EGR unit. we did this because we didn't want to purchase new parts only to find that they were not necessary.
well...the use part worked and has been fine since.

for you...i don't think that the reg to premium fuel caused the problem.

 

[mike96]

(reset--been driving)....The sel has not come on so far 100miles (knock on wood)different driving cycles,no 0401 code ..Do U think i could run a function test obd11 to see if all scans good without muffing up test cycles,?& if so ,,suggest to take it in 4 inspection??

 

[mike96]

Passed inspection...

 

[S-H-O-Man]

My 99 SHO is having this same problem. I replaced the DPFE sensor this morning and had the light/cleared - it was a P0401 - EGR insufficient flow detected. The light came back on within 5 miles. Do you think it is my EGR valve? the car has 116,000 miles on it? thanks
Rob

 

[SHOZ123]

Valve might be dirty. Try applying vacuum to the vale directly when then car is at idle. should stumble.

Could also be the EGR valve vacuum solenoid or the small hoses.

 

[Mr Anonymous]

EGR valves almost never fail.

99 times out of 100 it's the result of the EGR passage in the surge tank being clogged.