automatic transmission won't shift into high gear ?

This could be a bad shift solenoid or wiring harness. Start by making sure your fluid is at the proper level and doesn't look black or burnt. If that checks out you will need a good scanner to get started with the diagnosis. If you don't work on your own car then use this link to find a good shop near you. https://repairpal.com/repair-shops Alex

AAMCO will scan for codes free of charge with no commitment to have it fixed there.