I have a 2003 Ody and the codes P300-306, 1456, and 1399 are coming up. The van just started running rough a week ago. I don't think this could have caused the problem, but I went 20 feet with my parking brake on. Just thought I would mention that just incase it might have caused it. I changed the spark plugs but the problem is still there. How could all six cylinders be misfiring at once? I don't think it would be the coils since it is all six. I thought it might be the distributer cap or rotor until I found out it does not have them. Any suggestions on the problem?