Q: I got a 05 pacifica and the head gaskets were bad so I changed them. I put it back together and changed oil and now it won't start.

Hi there. The codes are coming up for the Oxygen Sensor, Oil Pressure Sensor, Evaporative Emission System Vent Valve, and the Air Conditioning Clutch Relay. Since all of these conditions are separate circuits and in different locations, I suspect that the main engine ground is not connected. Check all the sensors and ensure that the are all plugged in and hooked up to the right sensors. Some sensor plugs are the same as another sensor and could be switched by accident. If you need further assistance with your electrical issues, then seek out a professional, such as one from Your Mechanic, to help you.