User`s guide

6 April 2012
High Wing Spoiler Center High
Mount Stop Lamp
The GM Accessory and Camaro
Transformer high wing spoiler Center High
Mount Stop Lamp (CHMSL) may develop
cracks in the area around the fasteners on
some 2010-2012 Camaros. If this condi-
tion is observed, replace the CHSML only;
it is not necessary to replace the spoiler.
The CHMSL kit is currently available
through the Warranty Parts Center. Refer
to #PI0685 for complete details.
The cracked CHSML can be removed
from the spoiler by removing the caps
that cover the screws, and then removing
the screws. Some force may be neces-
sary. Unplug the CHSML from the wiring
harness and connect the new CHSML.
The kit includes washers to be used with
the new CHMSL fasteners. It is recom-
mended to use Butyl to hold the washers
in place during installation of the CHSML.
The washers are designed to prevent the
cracking from reoccurring. Be sure to
tighten the screws to specification.
Thanks to Ann Briedis
Cracks in the area around
the CHMSL fasteners.
Diesel Exhaust Fluid Quality Poor Message
An Exhaust Fluid Quality Poor message
displayed on the Driver Information Cen-
ter of the 2012 Express, Silverado, Sa-
vana,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 associ-
ated with a specific contaminate.
•Windshieldwashersolvent–orange,
purple or blue
•Enginecoolant–orangeorgreen
•Engineoil–brown
•Transmissionuid–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 indi-
cate 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 1.310–1.3843 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 mes-
sage is displayed without any set DTCs,
diagnose the condition using the appropri-
ate 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
Washers are included with the
new CHMSL kit.
Inoperative
Cruise
Control
On some 2007-2012 Avalanche,
Silverado, Suburban, Tahoe, Sierra,
Yukon, Yukon Denali, Yukon XL,
YukonDenaliXLmodelsequipped
with a Trailer Brake Controller (RPO
JL1),thecruisecontrolmaybe
inoperative and the Trailer Brake
Control Module may set DTC B3894
(Stop Lamp Switch Circuit Plausibil-
ity Failure).
If normal diagnostics do not lead
to a correction, check the Master
Cylinder Pressure Sensor parameter
listed in the Trailer Brake Control
Module data list. If it is display-
ing pressure with no brake pedal
input, there may be a concern with
the master cylinder pressure sen-
sor, wiring/terminals, or Electronic
Brake Control Module (EBCM).
TIP: On models with Stabilitrak
(RPOJL4),themastercylinder
pressure sensor is internal to the
Brake Pressure Modulator Valve
(BPMV)/EBCM.
Thanks to Scott Fibranz