Flashing CEL

I've had a constant CEL on for a while now and the code I continue to get from it is P0500, speed sensor. The speedo and the tach also don't work, along with the cruise control. That all kinda made sense to me if it was in fact a speed sensor. So I replaced the speed sensor, there is only one at the transmission because it's a non-ABS truck, but it did not fix the CEL. So Ive just been living with it because I have no idea what it could be. Fat forward to today, about 40 minutes ago, I'm driving home, and outta the blue the VEL stars flashing, sometimes fast sometimes slow, just totally random. No rough idle, no hesitation, the truck is running excellent so I have a hard time believing it would be a misfire, which is what a flashing CEL usually means. It's really hot here today, I dunno if that makes a difference. But I just really can't deal with something like this right now. Any input would be greatly appreciated. Thanks a lot

 

Flashing CEL to my knowledge means misfire if you haven’t recently I would change plugs wires etc.

 

Flashing means damaging misfire, usually a leaking injector. Don't drive it if its flashing.

Pull codes to start, inspect spark plugs.