Diagnostic Tip - Exhaust Fluid Quality Poor Message Difficult To Clear

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DEF Quality Low Message

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3. higher than NOx1. 7. This document assumes that the DEF injector volume has been v erified and passes with 3 distinct spray plumes from the injector. 8. This document also assumes the intake and exhaust system are leak free. Intake and exhaust leaks can cause changes to the dos ing system performance due to varied NOx output from the engine. 9. After-market components includi ng, but not lim ited to, air in duction parts, performance modifiers, grill covers, and exha ust modifications may negative ly influence the DEF system performance. If all conditions above appear to be functioning n ormally, SCR replacement may be required but is a very rare o ccurrence. If the SCR is replac ed, the new component will require a DPF service regen fol lowed by the RFQT procedure prio r to releasing the vehicle. Also, refer to the SI for appr opriate resets to be performed by the Tech2. Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without com pleting every step, the remain ing steps do not need to be p erformed.

2. to be soaked in a warm garage for greater than 6 hours with the key off continuously. After this 6 hour key off event, make sure the DEF tank temperature is above -7C/20F immediately after key on. If not, it is necessary to repeat the soak procedure allowing t he DEF tank to warm up above the - 7C/20F threshold. N ot e When parking the vehicle outside t o perform the RFQT it is impo rtant to monitor the ambient temperature. If the MAF senses i ntake ambient temperature below -7C/20F the test may not run correctly or timeout. The Reductant Fluid Quality Tes t (RFQT) may not pass the first test or it may time out (45 minutes for LGH, 70 minutes LML). If th e RFQT does not pass, run a DPF service regeneration followed by an ECM power down and then another RFQT. If after 2 attempts of this total procedure, the RFQT does not pass, it is probable a faulted condition still exists with the vehicle. An ECM power down is required betwee n repeated RFQT tests (Key off, remove the ignition key, and unplug the Tech 2 for up to two m inutes between tests). It is important to note whether a n RFQT passes/f ails versus a t imeout event. Each of these could have a different root cause. For t he case in which the test tim es out, one or more of the Conditions for running the DTC (as stated i n the P20EE) were not met. Ther e will not be any indication on the Tech 2 for which condition was not m et. For the case in which t he test fails, it is necessary to inspect the DEF system/components for sy mptoms of failure. The followin g guides can be used to help p inpoint the suspect component. 1. During the RFQT, the downs tream NOx ppm should read roughly 7 0% less than the upstream NOx ppm on a healthy system. (As a n example the upstream NOx pp m should be near 100ppm when the downstream NOx s ensor 2 is around 30ppm or less ). 2. During a DPF regeneration, the SCR is too hot to reduce NOx e ffectively. The upstream and downstream NOx ppm values should be relatively similar. NOx2 ca n be up to 30% higher than NOx1 in some cases. 3. During a road test at highway s peeds (with system at operatin g temperature), the downstream NOx sensor should be 70% less than the upstream sensor and tran sition in the same direction as the upstream sensor, but at a much lower magnitude. During a road test, you can collect transient data for NOx1 and NOx 2. After a heavy acceleration fo llowed by a tip out (0 pedal), both sensors should go to zero w hile coasting down. If NOx2 doe s not go to zero shortly after NOx1, NOx2 is either faulty or the system is saturated with DEF . Performing this test during or shortly after a DPF regen prev ents the system from being sat urated with DEF. 4. If the above NOx sensor compar isons aren’t true, there are se veral possible causes. The NOx sensor cannot distinguish betwee n NOx and liquid NH3 (DEF). Hig h NOx sensor 2 readings can be caused by DEF getting past t he SCR catalyst. This can be the result of a degraded SCR catalyst or a condition that cause s excessive DEF in the SCR. A fter a DPF regeneration, the SCR system is purged of excessive DEF. It is easier to evaluate if an SCR brick is compromised right after a regen eration because it eliminates th e extra DEF that the system was exposed to. 5. The SCR system can also store NOx in cold tempe ratures (exten ded idle). When the system warms up, this NOx can be rel eased and results in a brief NOx2 increase above NOx1. 6. If NOx2 is malfunctioning or poi soned, NOx 2 values will be i nfluenced and may be stuck

1. Diagnostic Tip -Exhaust Fluid Quality Poor Message Difficult To Clear 2010 - 2015 Chevrolet Expr ess and GMC Savana 2011 - 2015 Chevrolet Sil verado and GMC Sierra Equipped with the 6.6L Duramax Die sel Engine RPO codes LGH or L ML This PI was superseded to update Recommendation/Instruction. Pl ease discard PIP5007D. The following diagnosis might be he lpful if the vehicle exhibit s the symptom(s) described in this PI. Condition/Concern A dealer may encounter a custo mer concern of an Exhaust Fluid Q uality Poor message displayed on the DIC. The dealer may or ma y not find DTCs stored. An Exhaust Fluid Quality Poor message can be displayed with no DTCs. The Exhaust Fluid Quality Poor D IC message notifies the custome r that the ECM has detected a drop in the SCR NOx r eduction efficiency. This PI is to assist with vehicles that have difficulty complet ing the Reductant F luid Quality Test (RFQT) and/or clearing the Exhaus t Fluid Quality Poor Message. Recommendation/Instructions Complete the current SI diagnos tic for any trouble codes or sym ptoms found. If an Exhaust Fluid Quality Poor message is displaye d with a specific DTC, use that specific SI diagnostic, and repair the vehicle as necessary. N ot e An Exhaust Fluid Quality Poor me ssage does not always mean the fluid is contaminated or needs to be changed. Use the J26568 - Coolan t and Battery Fluid Tester to test the fluid before deciding to discard it. If the dealer has found an Exhaust Fluid Quality Poor message w ith no DTCs, diagnose the condition using the current SI diagnosis f or DTC P20EE / P207F (P2BAD for 2012 and newer Model years). After making repairs use the SI D ocument titled "Reductant Flui d Quality Test (With or without DTCs)" to evaluate and clear the Exhaust Fluid Quality Poor DIC message. If the Reductant Fluid Qualit y Test does not complete, or the E xhaust Fluid Quality Poor DIC message is difficult to clear, pl ease follow the description an d suggestions below. General Information/Helpful Guidelines: If the vehicle has been in a c old climate condition, defined as -7C/20F or less over the last few days, it may be in “frozen tank status” which prevents the Reductant Fluid Quality Test (RFQT) from evaluating a result when trigge red. Frozen tank status is enter ed when the vehicle key on event reads a DEF tank temperature below -7C/ 20F. The DEF tank temperature may be warmer after extended idles but onl y the conditions at ke y on are considered. To exit “froze n tank status”, the vehicle n eeds

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