420sel Failing Emissions

[shinji]

I have a 420sel Mercedes Benz and it failed the last emissions test. The last HC ppm reading was 1717 where the limit is 91 and also the CO % reading failed to pass the limit was 0.50 and the reading was 0.54, this was from the ASM tail pipe test.
Is there anybody who can help me with the steps I could go though to fix this problem