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chessy56 11-12-2017 04:42 PM

P140B code
I'm getting a P140B code on a L5P Dmax, suggesting the EGR valve response is slow. Now, this code is being read on an older model Edge monitor which was originally used on my old LB7 2001. I have NO check engine light at the moment. I can clear it, but it reappears the next time I read the DTCs. Should this be something to be concerned with or just a false alarm?

rapidoxidationman 11-12-2017 04:59 PM

Do you trust your local parts store guy enough to let him put a (hopefully newer) reader on your truck to see if he can pull the same code?
Edit: On a 2017, wouldn't the factory warranty be valid enough to bring the truck to the dealer and let them sort it out?

chessy56 11-12-2017 05:15 PM

I can ask one of our guys at work who are product support engineers if they've got a moment to look at it. If the check engine isn't on, I wouldn't have known about it and am thinking it should be looked at, but it's not suggesting immediate action. I saw this code earlier in the week, and the check engine lamp did come on. However, after the 3rd restart, the lamp did not return and I've put some 450 miles on it since- and still no check engine lamp.

Thanks for the reply BTW...

chessy56 11-14-2017 08:39 PM

P140B diagnosed....
OK- P140B confirmed via TechII. One of our product support engineers @ GM noted the code in the history; my Edge was reading it correctly. Took it to the dealership and further diagnosis suggested that there was "too much air flow" at the EGR and hence, the code. However, I do recall that we got a bit of snow on the day the SES lamp was set (I probably pushed some into the duct when I was cleaning off the hood). My tech mentioned that the air induction system facilitates an accumulation of snow on the air filter- which should've restricted the air flow (odd that "too much" flow was being reported). I guess GM hasn't addressed the potential for snow to be sucked into the air induction intake yet (short sighted, IMO).

I tried getting a replacement air filter to keep in the event another blockage occurs. Sadly, no one carries one- not Auto Zone, CarQuest, NAPA nor my Chevy dealership! No dealership in my general area stocks one! You'd think that after 1 year since introducing the L5P, dealers would have one of these on hand. Also, the owner's supplement for the Duramax has a GM p/n 84030829 for this filter; however, my dealership states the number should be 84130829- a typo in the owner's manual as well?

I was thinking about a K&N replacement element, but that faces the same risk for getting plugged with snow too if GM doesn't address this issue. Just a heads up for you L5P owners operating in cold/snowy climates....

DmaxMaverick 11-14-2017 10:02 PM

Likely just a sensor anomaly, due to the snow, although any number of conditions could cause it. This condition was common with early LB7's when (cheaper) aftermarket or homemade intake plumbing was installed. The change in flow turbulence causes the MAF to misread the actual air volume. Some higher, some lower. The correct volume would still flow, but the sensor simply didn't read it correctly. The emission system sensitivity of the later models would certainly detect the slightest variation. The soft code (no SES lamp) may indicate the values are nearing a threshold value, but not quite crossing it.

More Power 11-21-2017 02:22 PM

Whether it's the variable vane turbocharger or variable position EGR, the position sensor can sometimes drift out of calibration. I technician with a Tech II scan tool can test the EGR system and re-calibrate the position sensor. The Tech can also exercise the related components to verify correct operation. Something to keep in mind.... Jim

chessy56 11-26-2017 06:55 PM

One more on this topic....
4 Attachment(s)
Happened again after a 6 hour drive in the rain- followed by freezing temps near Lake Superior. Same code. Took out the air filter, let the filter sit inside the house overnight and reinstalled (pain in the azz to install when everything is "cold"). After the 3rd start w/o an error, the check engine lamp went out & hasn't come back on (yet).

Also noted the Delco and GM p/n for this air filter, as posted in the owner's manual, are wrong! From the actual filter itself:
GM p/n 84262965; Delco p/n A3231C

Odd shape to this filter (opposing corners are NOT 90 deg angles), with a pre-filter foam mounted to the paper pleats. Pics attached.

DieselDavy 11-27-2017 09:36 AM

I am surprised by the filth of the pre-filter foam. How many miles are on it?
(I hope you are going to report this incident to the GM folks)

chessy56 11-27-2017 04:11 PM

That filter has ~ 37K on it. Yep, 37K miles (90% highway) and not even a year old. I believe the owner's manual has the change interval @ 45K miles. Even still, none of the dealerships in the area seem to have one of these in stock. I can't believe that after nearly a year since its release, some dealerships don't have routine replacement parts- like air and fuel filters! I may have better luck on-line somewhere.

And, when I raise the issue with Chevrolet (owner's site), I usually get the "refer your issue to the dealership" response. Come on Chevy- I know you've got people who monitor this site. How about a response!!!

cabletech 11-27-2017 05:47 PM

Rock Auto has the AC Delco filter for just under $22. Amazon lists the same filter for $30. I bought one from Rock Auto as a spare. Mine has been driven in 2 snows storms with no problems.


chessy56 10-25-2018 02:36 PM

I'm going to throw one more post on this topic as I've been getting these P-140B errors on and off for some time. I got another about a month or so back which made me look at the air filter- it was dirty and within a few thousand miles of its recommended change interval. New filter, cleared the error code and all was OK until driving in heavy rain at highway speeds weeks later- it came back again.

My dealership tech states that GM came out with a bulletin late September stating that they are looking into this issue but don't have a solution yet. GM is telling dealerships to clear the code, make sure the MAF sensor is clean, only OEM air filters are being used (no after market stuff) and send the customer on their way. I'll check with the dealership in a few weeks, but it appears GM is OK with ignoring the check engine lamp if it's only a P-140B.

DmaxMaverick 10-25-2018 07:28 PM

"Too much airflow at the EGR", coupled with intake air filter issues with rain/snow, suggests the filter restriction is causing the EGR to pass too much exhaust gas (air?) in to the intake. Earlier models had issues with too little EGR passage with some aftermarket intake systems/filters that had too little restriction. All of this may be "perceived", by the sensors, having been fooled by intake air restriction or redirection (which can fool the MAF). If the airflow numbers don't match up, it triggers a fault, real or not.

It is not uncommon for a dealer tech to suggest clearing a code and just driving it if the condition isn't harmful. If the engine runs and responds normally otherwise, it isn't likely to be harmful, at least in the short term.

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