Silverado Classic SS V8-6.0L (2007)
PROM - Programmable Read Only Memory: All Technical Service Bulletins
Engine, A/T Controls - Hesitation/Low Power
Bulletin No.: 07-06-04-034
Date: December 18, 2007
TECHNICAL
Subject:
6.0L (LY6/L76) Engine - Low Power, 4L70/4L80/6L90 Automatic Transmission - Hesitation, Difficult to Obtain Downshifts (Reprogram TCM and/or
ECM)
Models:
2007-2008 Chevrolet Avalanche, Silverado, Suburban, Tahoe
2007-2008 GMC Sierra, Yukon, Yukon XL
with 6.0L V8 Engine (VINs K, Y - RPOs LY6, L76)
and 4L70/4L80 4-Speed Automatic Transmission (RPOs M70, MT1) or 6L90 6-Speed Automatic Transmission (RPO MYD)
Condition
Some customers may comment that the vehicle has a hesitation or lack of performance. They may also comment that it is difficult to obtain transmission
downshifts. These conditions may be more pronounced when operating during high ambient temperature.
Cause
Causes that can contribute to these conditions include:
High intake air temperatures that reduce the engine's volumetric efficiency and can reduce the amount of spark advance available, which further reduces
power.
Operating with oversized tires - which have the same effect on the vehicle as numerically reducing the final drive ratio, thereby reducing the available
torque.
Engine or transmission calibration balanced more toward detonation prevention and fuel economy.
Improper axle ratio for operating conditions.
Comparison to previous vehicle with higher displacement engine (Big Block L18) or different final drive ratio.
Correction
Updated ECM and TCM calibrations are now available to address these concerns. Reprogram the specified controller(s) with updated calibration files
using the TIS2WEB Service Programming System (SPS) application based on the engine and transmission combinations listed below. As always, make
sure your Tech 2(R) is updated with the latest software version.
These calibrations will be selectable. Be sure to select the correct files for the vehicle you are programming.
LY6 (VIN K) Engine and 6L90 (MYD) Transmission
Reprogram the ECM with an updated engine calibration. This calibration will receive an alternative spark table to optimize available torque. Some
audible spark knock may be heard under severe applications. Minor spark knock under severe operating conditions should be considered characteristic
for this alternative calibration.
Reprogram the TCM with an updated transmission calibration. This calibration will make downshifts available more readily in the 64-80 km/h (40-50
mph) range, and during low speed throttle apply.
These calibrations will be available as an ECM/TCM programming sequence event. From the controller list, select "ECM/TCM (Automatic
Transmission Only)".
There are 2 calibration part numbers that are "selectable" for each controller. Read the description to determine the correct calibration for this condition.
LY6 (VIN K) Engine and 4L80 (MT1) or 4L70 (M70) Transmission
