Last answer is bang on! If you want more tests, this will keep you busy!

Jack up truck with drive tire off the floor.
2. Manually turn the drive unit to the
straight ahead position.
3. Run LEARN Steer.
4. Observe the response of the steering
system and select the symptom below to
start troubleshooting the error.
a. The drive unit turns to the left
mechanical stop. Once against the stop,
the sound created by the steering
system as current to the steer motor is
increased is heard. Release the
deadman and press the ENTER button
to abort LEARN no more than 8
seconds after the stop is contacted.
Failure to do so can cause damage to
the steer transistors. This indicates a
failure in the Steer Feedback Encoder
circuit. Refer to Diagnosis and Repair in
Test I22 - Steer Position Encoder Count

b. The drive unit turns quickly to the right
mechanical stop. After contacting the
stop, power to the steer transistors is
removed very quickly and the system is
shut down. This indicates a failure in
the Steer Home Prox circuitry.
Troubleshoot per Test I24 - Home
Position Proximity Sensor
c. No movement is detected in the drive
unit but the steering system can be
heard trying to turn the drive unit.
Troubleshoot the steer motor and
gearbox or the drive unit for binding.
d. No movement or a small amount of
movement is detected in the drive unit
and a constant noise cannot be heard
from the steering system. This indicates
an open in at least one side of the steer
motor power circuit. An open in the half
of the power circuit activated by T1 and
T3 base leads is identified by the drive
unit moving just enough for the Home
Prox to transition from metal to no
metal. At this point the steer system
will shut down and no other
movements can be made. An open in
the half of the power circuit activated
by T2 and T4 base leads is identified by
the drive unit moving just enough for
the Home Prox to transition from no
metal to metal. At this point the steer
system will shut down and no other
movements can be made.

Thanks alot. I'll take a look.

Essentially the truck does not know where the drive unit is positioned. This can be caused by a failure of the steer prox switch at the base of the drive motor. If you have alot of play in the ring gear of the drive unit the prox may fail to see the sensor rail intermittently. I've also had this code pop up when the drive unit mounting bolts came loose as well.