I'm getting the feeling that something is going terribly wrong here, so could you please elaborate a litte what you are trying to acchieve.
Putting resistor in series; you just add the values. 4pcs 6Ohm resistor make 24Ohm.
Putting identical resistors in parallel; divide by quantity. 4pcs 6Ohm resistor make 1.5Ohm.
Since U=RI and P=UI=U^2/R=RI^2
If you have a 48Ohm resistor and put 1A through it, you have also 48 Volts across it. Something that your ecu can not supply.
Also, if you use 48Ohm and an injector in series, the injector will surely not open oen bit, when 12V is applied.
If you apply 1A through a 48Ohm resistor, you will generate 48W of heat in the resistor, again something that of course will never happen in a 12V system.