Hello I would like to help you with this.
The fact that you cannot read the engine codes tells me that you could have a problem with your engine control model. Not the body control model.
If this was a security issue when you try the starter car it would sound like it was going to start and then die.
When you tried to jumpstart it with the battery charger it is very possible it damaged the engine control model. When your battery is dead and you try to use the high charging current it can create too much voltage because the current has nowhere to go. And this can fry the engine control model. This exact thing happened on my jeep and I had replaced the module.
It is best to use another car to jumpstart the dead battery and use a battery charger just for charging purposes on the lower settings
Making the fuel pump run will not make the engine run.
I also have been working on saturn's for many years specifically the SL series.
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