1991 300e 3.0 Lt. Pls someone help me kind of new to some thing on my repairs on this car. The check engine light came on so i changed the 02 sensor, them it went off for about a week, then back on again. I need to know how to find out what's real problem is, step by step with locations of where to check. Read in other threads about 8pin,16pin, not sure what is being said. Thank you!!!!!! HELP!!!!!!!!! SOMEONE!!!!!!!!