96 f150 351/e4od. Friday I drove it to the track and once I was on the highway I noticed it revving too high. So turns out the converter isnt locking up. I have a 3 way switch set up to either be stock/unlocked/locked and if I put it into the lock position it locks right up but won't lock up in the stock position. Any ideas what could be wrong?

 

That indicates that the PCM isn't calling for it to lock. It probably is one or more sensors are sending data indicating to not lock. It could be a bad bulb in one of the three brake lights, too.

 

im with Mark,i like to tackle and rule out the easy things first.another quicky;
or a bad brake switch (BOO) on the brake pedal.

edit,and don;t take for granted your custom lock up switch isn't prone to failure either.may want to bypass this next,hooking up the (what it is,the purple wire with yellow tracer iirrc?) back up directly to rule this out.

 

I forgot to mention I bypassed the switch and it made no difference. How would I know if the brake switch is bad? 3rd brake light works I'll try to check the rear brake lights now

 

Ok I checked the brake lights and they are all working as they should. Also cycled the hazard switch as I read somewhere that is an issue as well. Also noticed when the switch is in the stock position it won't lock up but the od light doesn't flash or throw a trans code. But when I force it to lock up even on the highway it throws a 743 code. So it seems the pcm doesn't want the converter to lock for some reason. I'm lost.