If the PLC won't go into RUN mode then you have an error. If you have a copy of the program I would try to clear the PLC memory and download the program. If this does not fix the problem, the TI 335 was private labeled from Koyo. Automation Direct handles Koyo products today http://www.automationdirect.com/adc/Home/Home
Although the 335 is no longer available, they may have a suitable replacement.
Good Luck
billwest
Bill West
Consulting Sales Application Engineer
Siemens Industry, Inc.
Industry Automation
Industrial Automation Systems
1900 Musket Court
Stone Mountain, GA 30087
Work: 770-310-5965