Let's think like the TCM in fourth for a moment:
FIPL input must be above idle to lock converter
Upon lock command monitor Tach and VSS
Use Tach for input RPM
Calculate internal trans gearing to figure output RPM based on VSS
Compare Input and Output RPM, must match within 50-100 RPM or throw code 62.
At this point I'd look from the sensors toward the tcm to rule out a mechanical issue. VSS and tach signals must be good for the TCM to even figure out if there is slippage.
FIPL input must be above idle to lock converter
Upon lock command monitor Tach and VSS
Use Tach for input RPM
Calculate internal trans gearing to figure output RPM based on VSS
Compare Input and Output RPM, must match within 50-100 RPM or throw code 62.
At this point I'd look from the sensors toward the tcm to rule out a mechanical issue. VSS and tach signals must be good for the TCM to even figure out if there is slippage.