those codes can be caused by bad contact tips or conections at cable terminals. you're probably not going to be that lucky because it can also be caused by the (cpu) the main contactor needs battery voltage to pull in then the voltage is lowered to somewhere around 10v to hold in and not overheat the coil. what happens sometimes is that the pull in voltage never happens so the contactor does not get fully pulled in. if you open the right side panel, turn the unit on, reach in and push the contactor manually and it pulls further in and locks you got a cpu problem. there is homemade relay / timer circuit that you can make but its a sneak attack and not a sanctioned repair.