problems with locked force motor current.

[trophystock]

Working on a 99 C5. when I start out driving the Force Motor Current (FMC) desired and actual change as they are suposed to. My FMC line pressure also changes. Now as soon as I go to full throttle and run thru the gears my FMC goes to 0 (actual and desired) and FMC pressure goes to 38%. They then stay there for the rest of the drive. they are locked at 0 and 38%. This makes for a very hard part throttle shift. Any clues? Should I be seeing higher then 38% at WOT. When changing the shifting values do I need to worry about the performance shift box or just the normal box since it is a C5?
Thanks,
Charles

[trophystock]

[jimmyblue]

If current is zero then you have full line. You can't have PWM
at 38% and zero current. 38% desired line pressure however
could map to 0 force motor current by the force motor table.

This seems like maybe an abuse, over-temp or similar
rabbit-hole. Might check that trans temp is not going nuts
and putting you onto a "hot" table or something. Look for
"peculiar" results on other sensors / PIDs wight where it
first "snaps" into the fault state. Like cars that lose the MAF
will go into a full-line mode, some models. Maybe there is an
intermittent that shows up at hard acceleration, puts a fault
and then you're stuck until next key-on. Might look and see
if any "immature" or transient DTCs are showing?

[JasonB]

Sounds like a bad force motor. The typical complaint is hard shifting that goes away when the key is turned off and when restarted goes back to normal until you hit high throttle again.