If you can convert or control the CSV format, you can force a column to parse as text in Excel by wrapping it in double quotes and prepending an equals sign.
Excel will carelessly discard precision in this format:
Value,0503E000,1234123412341234
Or even this format:
Value,"0503E000","1234123412341234"
Converting it to:
Value | 5.03E+02 | 1234123412341230
However, adding the equals sign forces Excel to begrudgingly preserve your data:
Value,="0503E000",="1234123412341234"
…which opens as:
Value | 0503E000 | 1234123412341234