what is 721_output speed circuit?
 

i have a problem on it with my X5(E53) and what does it mean

actually the problem is P0721 but how do i repair it

i had the same error and it's coupled with a funny acting transmission.

have you gotten anywhere? i was thinking of replacing the internal pulse generators and cabling inside the trans, and / or the crankshaft pulse generator that is on the bell housing.

has your trans been slipping / fail safe?

Mine has! I replaced the filter and replaced oil with Pentosin. Is there a way to check the transmission ECU before replacing it? My plan was to replace all transmission sensors and the wiring harnesses to know if my problem is mechanical or not. Does this sound like a good idea? How many sensors are on a 2001 4.4i transmission. Any help would be greatly appreciated.

Hello? Help a brother out! I am getting codes:

49: Symptom gear check
52: Gear check 2
59: Stalling speed
54: Gear check 4
50: Gear check 1

OBD2 codes are:
PO20
PO31
PO32

Thanks guys.