reseting codes
 

i have codes 6 17 20 that was shown i reset them but they have reappeared once i make the code reader what do i do next to clear them in the 38 pin

What year & model car??

code reset
 

mb doc its a 94 e420

If you are talking about the DM / diagnostic module you can reset them from the built in pushbutton/LED on the 8 pin ancillary diagnostic connector. But the procedure is the same for both for the pushbutton and the code reader - after reading the code hold the button down for 8-10 seconds, then turn off the ignition.

Turn off key for at least 10 sec , then ON for 10 secs, then start.