Technical Service Bulletins

GM trans update

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GM trans update

For the 2009 model year, several control changes were made to the 4L60E, 4L65E and 4L70E four-speed automatic transmissions used in RWD Chevrolet Avalanche, Colorado, Express, Silverado, Tahoe, Trailblazer, Trailblazer SS and GMC Canyon, Envoy, Envoy Denali, Savana, Sierra and Yukon, and Saab 9-7X models.

The valve body casting has been changed and will not back-service due to the removal of the pressure switch manifold (PSM).

A new internal mode switch (IMS) has been added (with deletion of the PSM). Do not reuse the roll pin that retains the IMS to the manual shaft. Do not remove the C-clip from the IMS, as this will damage the part.

The manual shaft has been redesigned to accommodate the IMS.

The actuator rod is a new design and will back-service. It has a flat on the rod to accommodate the IMS.

The wiring harness has been changed and now has the temperature sensor in the harness with a gray connector. Both the 20-way connector and the 6-pin connector for the IMS are now blue in color.

The following are new DTCs that have been added for the IMS:

  • P1820 (Internal Mode Switch A circuit low voltage)·
  • P1822 (Internal Mode Switch B circuit high voltage)
  • ·P1823 (Internal Mode Switch P circuit low voltage)
  • ·P1825 (Internal Mode Switch invalid range)
  • ·P1826 (Internal Mode Switch C circuit high voltage)
  • P1915 (Internal Mode Switch does not indicate Park/Neutral during start)



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