OBD code for newer eec(s)
624: Solenoid/circuit failure -Electronic Pressure Control (EPC) current is high – Transmissions 624 could be an ELECTRICAL fault, not a mechanical or hydraulic problem. You probably have a wiring problem (bad connection, corrosion, faulty solenoid, or PCM)
Most the time Transmission codes are bad solenoid packs more then bad transmissions. I had my Pack replaced recently for ~$600 at the local transmission shop. If I were in your shoes I would take the time to inspect all the wiring before stopping by the trans shop.