A/T Controls - Harsh Cold 2-3 Upshift/Busy Shifting
Bulletin No.: 07-07-30-021Date: August 23, 2007
TECHNICAL
Subject:
6L90 Automatic Transmission 2-3 Harsh Upshift with Cold Transmission Fluid Temperature, Busy Shifting When Towing (Reprogram Transmission Control Module (TCM))
Models:
2007 Chevrolet Silverado
2007 GMC Sierra
with 6L90 Automatic Transmission (RPO MYD)
Condition
Some customers may comment on the following conditions:
A 2-3 harsh upshift that occurs only when the transmission fluid temperature is between approximately -20°C and +25°C (-4°F and 77°F). After the transmission fluid temperature warms above this temperature, the condition is not present. Transmission fluid temperature can be monitored through the driver information center (DIC) to verify these temperatures.
Busy shifting when towing a trailer and using Tow Haul Mode. This condition will typically occur on 4-5 upshifts and 5-4 downshifts.
Correction
A revised transmission calibration has been developed to address both of these issues. Reprogram the TCM with an updated software calibration. This new service calibration is available on TIS2WEB using the Service Programming System (SPS). As always, make sure your Tech 2(R) is updated with the latest software version.
This revised calibration will only correct a harsh 2-3 upshift when the transmission fluid temperature is within the specified temperature range and busy 4-5, 5-4 shifts when towing and using Tow Haul Mode.
After reprogramming the TCM, Service Fast Learn Adapts must be performed using the Tech 2(R). Check and clear all DTCs that may have set as a result of the programming process.
Reprogramming a control module with the same calibration is not considered a valid repair.
Warranty Information
For vehicles repaired under warranty, use the table.
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