A Check Engine illuminated yesterday in my driveway. Nothing seems wrong with the car, and that's not what this is about. When I tried to read the codes, I only got a solid red while pressing the button. I tried all available jumper positions, and it was the same solid red regardless of how long I held the button. Same solid red even with jumper disconnected. This was initially with ignition in ACC, but I repeated with it in ON (pos 3) to same effect. I used the diagnostics once, about a year and a half ago, and successfully retrieved and cleared an emissions code.

So any thoughts on how to fix my readout? Since I got the check engine light, I presume the diagnostic itself is working. For what it's worth, failing to read or clear the code, I did the ol' disconnect the battery, and the light has not come back on, so I'm not losing any sleep over that. I just want this system working for when and if I have a larger problem in the future.