21-013-15

Flash: AS69RC/AS66RC Transmission Shift And Diagnostic 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 conditions. Vehicles equipped with an AS69RC automatic transmission (sales code DF2) ? Less than desired towing performance while using cruise control. ? Harsh engagement while shifting from neutral to drive, neutral to reverse, or park to reverse with vehicle still in motion (rolling garage shift). ? Transmission Oil Temperature light illumination during high engine and tow loads. ? Engine flare during 2-1 tip in downshift. ? Less than desired shift quality during 6-5, 5-4 coasting downshifts. ? Delayed downshifts in Tow/Haul mode while driving down grades. ? Less than desired transmission shift performance when transitioning from low traction surface to high traction surfaces. (i.e. ice covered road to clear pavement). ? Harsh 2-1 downshift. ? Less than desired shift points during light pedal and Wide Open Throttle (WOT) operation or while in Tow/Haul and engine brake modes. ? Delayed engagement when shifting from neutral to drive, neutral to reverse, or park to reverse (garage shifts). ? Audible squawk noise on 4-3 downshift. ? Poor vehicle acceleration in first gear with vehicle fully loaded. ? Malfunction Indicator Lamp (MIL) illumination with no defect found for Diagnostic Trouble Code (DTC) P253D - PTO Sense Circuit High. AS66RC automatic transmission (sales code DF3) ? Transmission Oil Temperature light illumination during high engine and tow loads. ? Less than desired towing performance while using cruise control. ? Harsh engagement while shifting from neutral to drive, neutral to reverse, or park to reverse with vehicle still in motion (rolling garage shift) ? Engine flare during 2-1 tip in downshift. ? Less than desired shift quality during 6-5, 5-4 coasting downshifts.