What's the fluid look like, red or brown (or black)...is it at the correct level? The trans has a hard time if it gets overheated and the fluid gets burnt. If the fluid is not the correct fluid (Dex/Merc) or not at the correct level, the trans can't do it's job. The fluid is not just lubricant, it's also hydraulic fluid. Makes the valve bodies go up and down, makes the torque converter work.

When is the last time you serviced it (changed fluid, filter etc.)

Changing the solenoids will likely help it out, but can be pricey. The CEL sounds like that the solenoids are having trouble working...but could be as easy as a fluid service. Your AW4 should last almost forever if properly maintained.