There is a TSB out on your truck, for flashing O/D off lamp and or diagnostic
trouble codes 645, 646,647, and 648 stored in memory.
This applies to 4R44E/4R55E trannys with engine calibration 5-58B-R10, 5-58R-R10
Service all non trans DTC's first, then service all trans DTC except 645, 646, 647
and 648. For these codes follow TSB 97-17-24.
For this TSB after checking the tranny and the Throttle position sensor and wiring,
verify the vehicle has the latest level calibration. If it does not, replace the
powertrain control module. This is the second and easier TSB if you have the codes shown and tranny buid date shown below...
Saturday, April 12th, 2008 AT 12:21 PM