In the middle of an exhaust swap, turned the car on, put it in drive to pull it out of the garage for the night, i noticed the D4 light wasn't working, but the D3 and 2 and 1 lights were. Does the problem have to do with the fact that i currently don't have a muffler on? I know I have a bad second O2 sensor, but i don't think that would make the D4 light go off?
any suggestions?
96LX Auto.