Engine - Sound Change In 3 or 4 Cylinder Mode
INFORMATIONBulletin No.: 06-06-05-001E
Date: October 17, 2011
Subject: Information on Change in Exhaust Tone or Sound for Active Fuel Management (AFM) System Equipped Engines 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
2007-2012 Chevrolet Avalanche, Impala, Silverado, Suburban, Tahoe
2010-2012 Chevrolet Camaro
2007-2009 GMC Envoy Denali
2007-2012 GMC Sierra, Yukon, Yukon XL, Yukon Denali
2007-2009 Saab 9-7X
Equipped with Active Fuel Management System Vortec(R) GEN IV 5.3L, 6.0L or 6.2L V8 Engine RPOs LMG, LC9, LY5, LH6, L76, L77, LFA, LZ1, LS4, L94, L99 or 3.9L V6 Engine RPOs LZ8, LZG
Please Refer to GWM/IVH
Supercede:
This bulletin is being revised to add the 2012 model year and provide tip to verify vibration. Please discard Corporate Bulletin Number 06-06-05-001D (Section 06 - Engine/Propulsion System).
Some customers may comment on a change in the exhaust note or tone when an Active Fuel Management (AFM) System equipped engine is in 3 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 Active Fuel Management System equipped vehicles and no repairs should be attempted.
Tip
For full size trucks, verify the vibration by test driving the vehicle at approximately 48 km/h (30 mph). Use the DIC to monitor AFM eight (V8) to four (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 the Active Fuel Management System is enabled, physical changes take place within the engine that allow it to run as a 3 or 4 cylinder motor 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 the Active Fuel Management System is only activated during steady state/near steady state driving or during coast down. In both of these situations, the load on the engine is minimal and general exhaust volume (sound) is low. You may give a copy of this bulletin to your customer.
Disclaimer