Well I started getting a CEL for O2 sensor Downstream unit. Replaced the unit had someone clear the code and it was OK for a couple weeks. No the CEL will come on for the same O2 sensor and will go out in about 70-100 miles stay out for a while and then come back on??? I think I may have a wire shorting out somewhere in the harness (not fun). Would anyone be able to tell me where to start looking or provide a schmetic of the O2 wire routing / color codes? Thanks.