Converter will lock up when trans is cold but not after warms up
 

Hi guys, I have a 96 4x4 lt. Im having problems with my converter not locking up. If I get in it after sitting long enough for the trans to cool down completely and get right on the highway it will lock up. But once it gets warmed up it wont lock up again. I just replaced the brake light switch, tcc solenoid, and filter. Any help is appreciated

Engine coolant sensor plays a role in inhibiting lock up. Just a thought.

Check for pending codes if no SES light is on. A lot of pending codes will cause the PCM to disable the TCC. It's one of the first things to go, especially with pending misfire codes. I know this from experience.

Ses is on but its from the oxygen sensor after the converter missing. No other codes. Would the temp gauge read properly with a faulty coolant temp sensor?

Yes it might as the gauge may be getting proper signal but PCM could be reading incorrectly. If you are just using a code reader you really need to get it scanned with a good scanner with up to date software. So you can read history and pending codes.