060605001H

Bulletin No.:
Service Bulletin
Date:
06-06-05-001H
March, 2019
INFORMATION
Subject:
Information on Changes in Exhaust Tone for Active Fuel Management Engines When in
Three or Four Cylinder Mode
Models:
2007 Buick Rainier
2007-2009 Buick Allure (Canada Only), LaCrosse
2007 Chevrolet Monte Carlo
2007-2009 Chevrolet TrailBlazer
2007-2013 Chevrolet Avalanche
2007-2018 Chevrolet Silverado
2007-2019 Chevrolet Impala, Suburban, Tahoe
2010-2019 Chevrolet Camaro
2019 Chevrolet Silverado LD
2007-2009 GMC Envoy Denali
2007-2018 GMC Sierra
2007-2019 Yukon, Yukon XL, Yukon Denali
2019 GMC Sierra Limited
Equipped with Active Fuel Management 5.3L, 6.0L or 6.2L V8 Engine – RPO LC9, LH6,
LMG, LS4, LY5, L76, L77, LFA, LZ1, L83, L86, L92, L94, L99, LT1 or LT4
Equipped with Active Fuel Management 3.9L , 4.3L V6 Engine – RPO LV3, LZ8 or LZG
Attention: This Bulletin also applies to any of the above models that may be Export from North
America vehicles.
This Bulletin has been revised to add the 2017-2019 Model Years to applicable vehicles.
Please discard Corporate Bulletin Number 06-06-05-001G.
Changes in Exhaust Tone
Some customers may comment on changes in the
exhaust tone when an Active Fuel Management (AFM)
equipped 6 cylinder or 8 cylinder engine changes to
3 cylinder or 4 cylinder mode. Some drivers may also
notice a very slight vibration in either the accelerator
pedal, floor pan and/or the steering wheel. This is a
normal condition for AFM equipped vehicles and no
repairs should be attempted.
Tip: For full-size trucks, verify the vibration by test
driving the vehicle at approximately 30 mph (48 km/h).
Use the DIC to monitor the AFM V8 to V4 cylinder
activation. Confirm the vibration is present during
V4 mode. Place the transmission in manual mode 5th
gear to force the engine to stay in V8 mode. Again
operate the vehicle at same speed and confirm no
vibration is present in V8 mode.
Customer Information on Active Fuel
Management
When Active Fuel Management is enabled, physical
changes take place within the engine that allow it to run
as a 3 cylinder or 4 cylinder with accompanying
additional fuel savings. The change in exhaust tone is
expected, as all sound from the exhaust is the result of
combustion in the engine. The ability to perceive these
changes in sound are kept to very minimal levels as
AFM is only activated during steady state or near
steady state driving conditions or during a coast down.
In both of these situations, the load on the engine is
minimal and general exhaust volume (sound) will be
less. Please provide a copy of this bulletin to your
customer.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these
technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper
service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a
job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your
vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the
information.
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