Re: error code 628 converter clutch error (E4OD)
Here is what I found on the internet. Doesn't look good.
Defective Converter Original Lock-up pistons (in the converter) often crack and/or warp creating internal leaks which prevent full apply of the Lock-up piston. The result is burned oil, black or purple converter, and possible Trouble Code 62 (or 628) stored in the computer memory.
Replace the converter Most converter re-builders are installing the updated Luk Lock-up piston which has proven to be resistant to cracking and bending. For some applications the original piston is being reinforced (welded) and reused. Typically, rebuilt converters with the new Luk piston cost more than those without it, but they are certainly worth it, especially in Diesels. (All RPM converters have the new piston installed).