Chevy and GMC Duramax Diesel Forum banner
1 - 2 of 4 Posts

· Registered
4 Posts
Discussion Starter · #1 · (Edited)
Hi All,

Looking for some help with my 2015 LML, currently in limp mode due to poor DEF quality, and the service bay quality test can't be triggered. I apologize if I get any terminology wrong, but this has been ongoing for awhile and as I write, am trying to recall from memory:

TL;DR: 2015 Duramax (stock), poor DEF quality, Limp mode, 154k miles, GM thinks DPF is bad, can't source part, was already replaced 50k miles ago, GM customer care doesn't help, 8 year old paper weight, don't know what to do next - don't drive enough/tow to justify the diesel, want to buy a half ton, can't take a huge loss.

I dropped by truck off for repair end of November 2022 at the local Chevy dealer. Prior to that, I had a CEL (P20EE) for a bad NOX sensor - this part was out of stock with GM, but I was finally able to source an OEM sensor from an online Duramax specialty store. This took care of my CEL, but had the display message of "Poor Exhaust Fluid Quality XX miles until 65MPH Limit". I borrowed my friends dad's Snap-On scanner and attempted to run output tests to do the "Service bay quality DEF check" without any luck, I filled the DEF tank with new DEF to hopefully solve the problem, no luck. I was able to force a service regeneration, as I read that could be part of the problem. After some searching for early LML, a Youtube video showed the reset needing to be done on a GM Tech2 device (or the later replacement device). Suspecting this was a Snap-On issue not being able to trigger the command, I made an appointment at the local Chevy dealer for what I hoped was a quick reset.

4 months later, the dealership has replaced the entire DEF injection system ( in Jan 2022 I had my local trusted shop replace the DEF heater, because I had a CEL, this fixed the problem) - the dealership agreed to warranty this part out as it was less than a year old. They ran multiple Regens but were not able to run the service test to clear the "bad DEF" code.

When the DEF injection system did not fix the problem, they opened a case with GM Technical support - they said to advice the client that the DPF could be faulty, and suspected poor diesel - they would recommend that to be replaced. The DPF was replaced on my truck 50K miles ago (under warranty) so I was surprised to hear this was the suspected path, and pushed back to GM customer cares. In addition, this part is not currently available according to the dealership. The dealer pulled the part, said it was damaged (picture attached) and believe the EGT temperatures before and after are not allowing the "service bay DEF quality" check to be run.

After many long and frustrating discussions with GM customer center, they have stated the truck is no longer in warranty, so they cannot buy the truck back, even though they are not producing the DPF at this time. They are able to offer a $5k good will offering off the purchase of a brand new truck. This is not acceptable, because I need to sell my current truck to purchase another, and can't afford to take a $20k loss on my current truck.

I have asked the dealership if they can install a used DPF (I have an acquaintance that has a spare LML DPF removed from his truck) but the dealer said it was illegal for them to install.

Even if the part was available, I hate to keep throwing money at replacing parts that doesn't actually fix the problem, and I am left further in the hole with a truck that won't travel over 4mph.

Any suggestions or comments would be welcome - I am currently at a loss of what to do next. Service has been lackluster at the current dealership, but I hate to tow the vehicle somewhere else to be told the same thing. I am still refusing to accept that a 8 year old truck should just be thrown away at this point in its life...



· Registered
4 Posts
Discussion Starter · #4 ·
Currently no CEL, just the message on the display that says poor DEF quality, and then it flashes to XX miles until XX mph limit.

Also this information was sent from the tech to GM technical:

Additionalinformationprovideo on t h ecall.
createoby: F76F60
C r e a t e d :
F A dD a t e :
DEF Qulity poor message
NewDieselExhaustFluidt and assembly and injector
Willnot pass reductant fluid qualitytest
will pasrepeneration
States EGI readingswere 1/950 - 1000 2/3/4all over 1000with egt3 being the hottest temp

Based on the Information providedTAC recommends

-Advised the dealer to check the fuel quality a C s per ServiceInformationdocument ID 2363452
-Advise to suspectDieseiOxidationconverter damage

Sent from my iPhone using Tapatalk
1 - 2 of 4 Posts