Duramax service emissions won’t reset

I’ve had some cases where it got this bad…. Tried to update ecm but wouldn’t let me because it was already at the latest calibration. One time I actually had to replace ecm and that solved it. Sometimes they get kind of locked and you have no choice….

I’ve ran into that once before where I had to replace the ECM but I was hoping someone else had an idea lol

These will be a big pain to do. i have run into this a few times and even the gm diesel techs say that some just do want to go. Basically you will need the vehicle to pass its fluid quality test. i would highly recommend doing the thermostats so the pcm has nothing to pick on. what i have done on some is doing a manual regen while driving for half hour and drive it hard. park in parking lot…

I‘ve tried sending a driver to go put some miles on but I didn’t give them any specific instructions like this. I’ll try this and see what happens. And everything looks pretty normal data wise except the coolant temp being low obviously. Hopefully doing that test drive process works. If not I may send it with the customer and see what happens cause he’s already made it clear he can’t afford an…

I wouldnt call an ecm over this. gm software engineers made these processes so hard and difficult to get around

I’ve been called in on 2 of these trucks acting the same. Try this: Go into the CPCM, Special Functions (bi-dir controls), and manually run each DEF heater on & off again. Then see if your fluid quality test will run to completion.

Hmmm that’s interesting because the service bay test always says it’s commanding the heaters on right before it aborts. I’ll have to try that. Thank you!

I Have had this issue multiple times as well. just turn each heater on for 30 seconds and usually clears the warning.

I’m going in today to try this cause it makes sense to me and I won’t be able to stop thinking about it if I don’t try it! Thank you!

REDUCTANT FLUID QUALITY TEST IMPORTANT: Many Techs are reporting a Tech 2 scan tool must be used to perform the Reductant Fluid Quality Test. (RFQT) Other scan tools will not complete the test. Circuit/System Description A Reductant Fluid Quality Test is required when an incorrect reductant composition is monitored or the NOx catalyst efficiency reaches a minimum threshold and a DEF quality…

Thank you!

The early LML's … are a bit of a bear to reset, but its doable. First off, like others have mentioned, you need to resolve the thermostat issue. All of the engines conditions are tied to emissions. The coolant temperature needs to be correct/at operating temperature for the reductant fluid quality test (RFQT) and the DPF service regen to work correctly…. you just can't fool the PCM…

I know the ECM doesnt have the newest update as I was wanting to do that originally but lack of tooling foiled that avenue for the moment. I didn’t think about checking all the speed sensors I was just watching the vehicle speed PID and saw it never moved so I was getting frustrated lol I’ll have to check that out when I get back to work Monday. I know it needs the thermostats I’ve just been…

Hi Blaine, What DTC(s) were originally set? Are there DTC(s) currently set? Do you have access to GM TSB …E?

I don’t know that TSB specifically but I can check on Monday. Originally the concern was a check engine light and an exhaust leak. Codes were pretty much all glow plugs, MAF frequency, and coolant below regulating temp. We replace the glow plugs and replaced the flange gasket and bolts behind the DPF But customer declined any other repairs (found out later he had a budget and the service…

I would also suggest like's been mentioned to go into GPCM and manually turn on the DEF tank heaters. Just had a 16 in the shop this week that the owner replaced the DEF tank heaters and couldn't get the message to go off in the dash. No codes relating to the issue just the message on the dash. Only way I could get it to clear was turn on the DEF tank heaters. Magically it took care of it.