Diesel Exhaust Fluid Quality Poor Message Conditions

The Exhaust Fluid Quality Poor message, sometimes followed by other Diesel Exhaust Fluid (DEF) messages, may appear on the Driver Information Center of 2010–2016 Express and Savana vans and 2010–2016 Silverado HD and Sierra HD models equipped with the 6.6L Duramax diesel engine (RPOs LGH, LML).


DEF quality-related conditions also may be found on 2016 Colorado and Canyon models equipped with the new 2.8L diesel engine (RPO LWN) and 2014-2016 Cruze equipped with the 2.0L diesel engine (RPO LUZ).


Diesel Exhaust System Components


F07 DEF system

Fig. 7


The diesel exhaust system includes the following components: (Fig. 7)


(A) Turbocharger downpipe

(1)  NOx sensor number 1

(2)  Exhaust Gas Temperature (EGT) sensor 1

(3)  Hydrocarbon (HC) injector

(B)  Diesel Oxidation Catalyst (DOC)

(4)  Exhaust Gas Temperature (EGT) sensor 2

(5)  Diesel Exhaust Fluid (DEF) Reductant injector

(C)  Selective Catalyst Reduction (SCR)

(6)  NOx sensor number 2

(7)  Exhaust Gas Temperature (EGT) sensor 3

(D)  Diesel Particulate Filter (DPF)

(8)  Exhaust Gas Temperature (EGT) sensor 4


Exhaust Fluid Quality Poor Message


There are various reasons why diesel exhaust system determines the DEF is poor quality, including a contaminated or diluted fluid, low-quality fluid or a frozen DEF tank.


Contaminated Fluid – While contamination could result from any number of fluids, it’s most likely that it will involve common automotive fluids. Owners may mistakenly fill the DEF tank with other fluids, such as DEX-COOL coolant (Fig. 8) or diesel fuel (Fig. 9). DEF should be a clear liquid. Test a sample from the reductant fluid tank and then refer to Contaminants in Diesel Exhaust Fluid Diagnosis in the appropriate Service Information. Use special tools J26568 Coolant and Battery Fluid Tester or EN50422 Diesel Exhaust Fluid Refractometer for fluid testing.


F08 DEF and coolant

Fig. 8


F09 DEF and diesel fuel

Fig. 9


Refer to #PIP5370 for additional examples of contaminated DEF.


Low-Quality Fluid – Clean, fresh DEF is critical for optimal SCR efficiency. SCR efficiency is determined by monitoring the nitrogen oxide (NOx) sensors located upstream and downstream of the SCR. When the ECM detects a drop in the SCR NOx reduction efficiency — suggesting a diluted or contaminated DEF supply — the vehicle alerts the driver with several prompts and warnings.


Once initiated, the warnings grow increasingly more serious as the vehicle continues to be driven. The vehicle’s current DEF quality warning status is displayed on the scan tool. When a drop in SCR efficiency is detected, the normally OFF Reductant Fluid Quality Warning Indicator Command will display certain Warning Levels (1 through 5), depending on the number of miles driven, the number of ignition cycles, and whether a refueling event was detected. The series of warnings alert the driver that system service is urgently needed.


If it’s difficult to clear the Exhaust Fluid Quality Poor message or complete the RFQT, refer to #PIP5007.


Frozen Tank Status – Another possible reason for the Exhaust Fluid Quality Poor message is whether the vehicle has been in a cold climate condition of 20° F (−7° C) or lower for several days, thereby triggering a Frozen Tank status. If this occurs, it may prevent a Reductant Fluid Quality Test (RFQT) from evaluating a result when triggered. The reductant tank temperature may be warmer after extended engine run time; however, only the conditions at key-on are considered.


To exit Frozen Tank Status, refer to #PIP4864 and Bulletin #10-06-04-013.


Other DEF-Related Messages


In addition to the Exhaust Fluid Quality Poor message, the following DEF messages may also appear:

• Service Exhaust Fluid System (Tamper)

• Exhaust Fluid Range

• Service Emission System


If any of these messages are displayed, refer to the Bulletin #12-06-04-002.


Order of Repair


If a combination of DEF-related messages or conditions exists simultaneously on a vehicle, an order of repair must be followed, using the Driver Information Center as the guide as to what needs to be corrected first.


The messages will always display in the correct order of repair. For example, if a tamper condition and a poor quality condition exist together, the Service Exhaust Fluid System message will display until the tamper condition is corrected. The Exhaust Fluid Quality Poor message will then display, which will need to be corrected next.


– Thanks to Larry Yaw

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