21-009-15

Flash: Transmission Shift And Drivability Enhancements This bulletin involves reprogramming the Transmission Control Module (TCM) with the latest available software. A small number of customers may experience one or more of the following concerns. These concerns are broken up per engine and transmission combination. 6.2L engine (sales code ESD) equipped with an 8HP90 transmission (sales code DFE) ? Transmission will not upshift during Wide Open Throttle (WOT) acceleration. ? Harsh or inconsistent coasting downshifts. ? Transmission will not shift into 7th gear during high speed driving. ? Inconsistent or busy shifts during stop and go traffic. ? Inconsistent gear shift patterns when driving on grades. ? Malfunction Indicator Lamp (MIL) Illumination during ABS activated stops with Diagnostic Trouble Code (DTC) P1DCD TCM Monitoring Processor Performance, Multiple Clutches Locked Up. 6.4L engine (sales code ESG) and equipped with an 8HP70 transmission (sales code DFK) ? Harsh or inconsistent 1-2 upshift. ? Harsh of inconsistent coasting 4-3 downshift. ? Harsh or inconsistent gear engagement when shifting to drive or reverse. ? Instrument Panel Cluster (IPC) shows the incorrect gear when in manual mode. ? Harsh of inconsistent shifts during tip-in acceleration from closed throttle. ? Inconsistent gear shift patterns when driving on grades. ? Inconsistent release of Hill Start Assist during tip-in acceleration. ? Transmission upshifts on sweeping curves under track driving conditions.