throwin code 0420 , need help!
#1
throwin code 0420 , need help!
About a month or two ago the service engien light in my 01 ws6 came on, i had it scanned and it threw two codes, one was 0420 and the other 1416, i replaced both air check valves(1416), and the light went off until about a few days ago, i had it scanned again and it threw 0420, what is that code, and what needs to be done, anyone?