21-027-15

Flash: Transmission Shift Enhancements This bulletin involves reprogramming of the Transmission Control Module (TCM) with the latest available software. A small number of customers may experience a Malfunction Indicator Lamp (MIL) Illumination. Upon further investigation, the technician may find Diagnostic Trouble Code (DTC) P0734 - Gear 4 Shift Incorrect Ratio stored in the TCM memory. In addition, the following TCM calibration improvements are also available for vehicles equipped with the 845RE 8 speed transmission (sales code DFL). These improvements are listed per engine application. 3.0L gas engine (sales code EHD) ? Improved upshift timing. ? Improved torque converter engagement. ? Improved shift timing during tow mode operation. ? Improved shift points during aggressive driving. ? Calibration improvement to correct bump feel during 2-1 downshift. ? Improved shift timing while in snow, base, and hill modes. 3.6L gas engine (sales code ERB) ? Improved 4-3 and 3-2 downshifts. ? Improved shift timing at higher altitudes. ? Improved shift timing while in sand mode. ? Calibration improvement for multi-gear downshift timing during passing maneuvers. ? Calibration improvement for intermittent delayed upshift.