98 V70xc P0740 and CEL turns on approx 12 miles after reset

[Grimace]

So I am getting the P0740 overdrive solenoid code (or whatever it is named specifically). When I reset the code the cars drives normal for around 10-15 miles. Car goes into overdrive like it normally should until the arrow starts blinking and CEL comes on.
Does this mean something other than pointing right to replacing the solenoid?
Is there a few things I can check, or I am looking at pretty much replacing it?

Brief history of the car. has 200k on it. PO did a bunch of work, including changing the trans fluid. I bought it with a bad head gasket, but it was drivable. Drove it about 24 miles before parking it to do the head gasket, no trans error light.
Car sat for about 5 months before I was doe working on it. First drive I got the blinking arrow, and that's where I am now.
I didn't have both ground straps on from the firewall to the head. I do now though.