LML "Service Exhaust Fluid System" No DTC's after DPF Re-Install

snowman22

Member
Jan 30, 2018
279
0
16
SoCal
I couldn't find any useful info on what would cause this so I figured I would put it out there after fixing it.

I had to re-install my factory exhaust and after doing so the system started a countdown from 99 miles to reduced to 65mph. The edge CTS didn't show any codes, so I figured I needed the GDSII. It also didn't show any codes and passed the full DTC and info test. Needless to say I was getting frustrated.

I started looking around in the system and found a line on "Reduced Engine Power History" that showed as "Reductant System Tampered"

Upon further digging I found a tab called" "Reductant System Malfunction Warning Service Bay Test" After running the test the system cleared itself and all is normal again. It seems like a fault test that will clear a previous issue even if there is no DTC.

Hopefully this helps someone someday...
 

TheBac

Why do I keep doing this?
Staff member
Apr 19, 2008
13,336
14
38
Mid Michigan
This probably would've helped the situation with my Cruze last week. Looks like Ive got to go get myself an MDI.
 

KyleC4

Tech
Dec 30, 2016
310
3
18
Bay Area
The Reductant Warning Service Bay Test is what we usually run once we’ve fixed the vehicle, DTC’s cleared and all that remains is a warning message on the DIC. Usually when a service emission system warning message came on. But hopefully in your case it has fixed the truck and there won’t be anymore problems. The system can be frustrating at times. And for reference the system has 11 levels of “Tampering” and each level has its effect on vehicle operation. Like reducing vehicle speed to 4mph, cause that’s needed.....lol
 

DuramaxMTBzn

New member
Jun 25, 2020
5
0
1
Hey @snowman22 , I have this exact same issue atm. I have a question for you, when you ran the test.. the vehicle had to be on correct? Did the vehicle do anything such as increase rpms etc? When I start the test my truck simply sits there doing nothing.
 

snowman22

Member
Jan 30, 2018
279
0
16
SoCal
I don't remember it doing anything noticeable. It just ran the test and showed it completed on the screen. Once it completed successfully it no longer had the message on the dash.

It seemed to be more of a system verification to allow the reset.
 

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