When i got my 1999 chevy venture van it was shifting really hard so i put some sea foam in and put it on my computer code i got was po742 so i reset comp to get rid of code and that worked till today i was driving it and the light come on again got same code so i reset again and test drove it and light is off and drives fine could someone tell me what could be wrong with it thanks

 

Transaxle code P0742 says the TCC release switch circuit was closed (indicating the TCC was applied) while the TCC was commanded off. The problem could be electrical like a short in the circuit or mechanical like a faulty TFP valve position switch, sediment in the valve body, faulty TCC mechanism, etc. Check the fluid level if you can and, if not that, take it in for service.