One easy solution? Not hardly...each fault code has different possible causes, and therefore different possible solutions:
P0087 stands for "Fuel Rail/System Pressure Too Low."
Potential causes of a P0087 trouble code may include: Weak fuel pump, clogged filter or screen, restricted fuel supply line, Faulty fuel pump driver module, Faulty fuel pressure sensor.
If vehicle is equipped with a fuel pressure test port at the fuel rail or line, check fuel pressure using a mechanical pressure gauge to determine if it is within specifications. Fuel pressure should also be tested under load with vehicle in gear or during acceleration. If fuel pressure is below spefications, visually inspect all fuel lines going back to the tank to see if there is a restriction such as a bent fuel line. The fuel filter may be clogged if it has not been changed for a long time, or the in-tank fuel screen may have become restricted or clogged - check for damage to the fuel tank that could cause the bottom of the tank to press up against the fuel pump inlet.
P0300 stands for "Random Cylinder Misfire"
P0304 stands for "Cylinder #4 Misfire"
P0420 stands for "Catalyst System Efficiency Below Threshold (Bank 1)"
It can either be caused by a faulty catalytic converter or a false alarm from any of the sensors.