Diesel Exhaust Fluid Quality Poor Message

An Exhaust Fluid Quality Poor message displayed on the Driver Information Center of the 2012 Express, Silverado, Savana, and Sierra equipped with the 6.6L Duramax diesel engine (RPOs LGH, LML) notifies the driver that the Engine Control Module (ECM) has detected a drop in the NOx reduction efficiency of the Selective Catalyst Reduction (SCR) system. The Exhaust Fluid Quality Poor message may be displayed without any set DTCs.


An Exhaust Fluid Quality Poor message does not always mean the fluid is contaminated or needs to be changed. The J-26568 Coolant and Battery Fluid Tester can be used to test the fluid before deciding to discard it.


1. Collect a DEF sample of about 150 ml (5 oz.) from the DEF tank in a clear container. The DEF sample should be clear with no obvious coloration when held up to a light.

As clean DEF is clear, contamination by any common automotive fluids will cause the DEF to exhibit a trace of color associated with a specific contaminate.

• Windshield washer solvent – orange, purple or blue

• Engine coolant – orange or green

• Engine oil – brown

• Transmission fluid – red or brown

• Diesel fuel – clear, yellow, green, red or brown

2. Observe the DEF sample. It should have an ammonia smell. Clear fluid without the presence  of an ammonia odor may indicate water or DEF diluted with water.

3. Measure the refractive index of the DEF sample using the J-26568 Tester. The refractive index of pure DEF should be between 1.3814–1.3843 at 20° C (68° F). If not within the specified range, drain the remaining DEF and refill the tank with fresh DEF.

4. If the DEF tests normal, perform the DEF Quality test with a scan tool. The DEF Quality test should pass. If the test fails, replace the DEF.


If an Exhaust Fluid Quality Poor message is displayed without any set DTCs, diagnose the condition using the appropriate Service Information diagnostics for DTC P20EE (NOx Catalyst Efficiency Below Threshold)/P2BAD (Exhaust NOx Concentration High–Unknown Reason). After making repairs, use the DTC P20EE/P2BAD repair verification and/or SI Document number 2614265 titled “Reductant Fluid Quality Test (with or without DTCs)” to evaluate and clear the Exhaust Fluid Quality Poor message.


– Thanks to Donald Langer


Updated May 21, 2014

One Response to “Diesel Exhaust Fluid Quality Poor Message”

  • paul:

    does this vary when you have an nox sensor error code but your def fluid is good or do you have to replace the selective catalyst

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