1988 XJ 6-cylinder Auto Trans Problem
 

My XJ is experiencing an issue where when the shifter is placed in "D" it stays in high-gear. Manually shifting to "1-2" or "3" still works. Problem persists regardless of vehicle speed or throttle position.

I've checked both transmission fuses, the one in the fuse panel near the driver side kicker and the one below the glove box in the passenger side, both are intact with no issues.

From what I gather, it seems like my TCU has gone bad. Any other things I should check before going off and buying a replacement TCU? I bought the thing a few years ago for $800 as a budget 4-wheel hunting rig and I'm reluctant to throw money at the problem.

Appreciate the help!

I would get one from the junk yard first. I got one for $20 couple months ago.

Yep. And get one from an 88 or later.