Yes and yes.

To be sure the OD won't work if the OD solenoid is not energized. The fastest way to check is verify power at the solenoid. I would also test the solenoid for continutity, the manual shows it has having 13 ohms resistance to ground.

The OD control system is the most common failure. A bad solenoid is easily changed. It's held on with two bolts and has two O rings under it. Trying another one is a low cost test.

Two other posibilities.

1: The Valve body.

2: The OD clutch has a bad seal or a bad clutches.

The valve body is easy to service in the vehicle. Most internal failures will be from bad seal that then kills the clutch pack. On the units I have rebuilt the OD always seemed to be in the best condition.

Kevin