I changed both fuel filter but now it will not start?

I bought used ambulance am trying to converted to an RV. I have small led screen shows volt 12.1 and amps when I turn the switch on start -202 after 15 second stop in this no -13 all minus (what is amps stand for). Suddenly the car wont start my diesel gauge shows I have little less than a quarter diesel in it. When switch is on I can here the fuel pump working for 10 seconds. When I start the car just crank would not start. Someone told me may be air in fuel system. I have 3 batteries installed. There is electric board and vanner invertor.
What should I do to start the car again?
Thanks a lot.

Thanks a lot. My car is an ambulance I just bought three new batteries vin: 1fdxe4fp5ada30421. I don't know if it helps I need to buy code reader, I am not sure if they sell it here if I could not find it can we try something else?
Thanks again

Thanks a lot I will check the battery ground and try to solve the code issue and get back to you if I succeed I will order one from amazon do you suggest piratical one with easy operating for none experience like me
thanks again

Thanks Mr. Ken. I have ordered the code reader I will received it within a week I have checked the battery ground cables and fuses every thing was okay. Then hi did something am not sure if it was right he open the hose filter and but little petrol in the part hose that going to engine the car start for one minute or less and stopped. He said there is air on fuel need to be out is he right and if he is how can I do it? I tried to find video same like my car but I couldn't. What's your advise?
Thanks a lot for trying helping me and your time.

Sear sir, I mange with somebody did this reading the first picture is last reading after he erased the second and third page codes the last one am not sure where is the ficm located. How to make sure this item if can be fixed or replaced? I hope I did send the picture right. Thanks a lot.

Thanks Mr Ken, frankly this is tough exam for me so I give my self F grade.
Every thing in my car was fine, I removed the steel shelves the chair the bed and the car still running my problems start when carpenters start to attached the wood wall to the frame with screw. After they attached the wall as you can see in the picture car did not start, but the light and rear air-conditions and refrigerator still run fine when switch key in on position. As you see in the picture. The 220 vanner invertor work okay. Someone told me because we worked inside and did not disconnect the battery?
Sorry for the long story but I thought may be you should know when and how the problems started. Diagrams hard for me to understand can we try something else like how can I test the (ficm) or does the ficm reprogrammed or replaced?Or if you suggest that I remove all wood wall and check wires again if this help.
Sorry again and thanks.

Thanks a lot Mr. Ken for your patient
today by coincidence while the technician checking wires I asked him to check the fuse box again we checked them they where all fine by coincidence he noticed one spot is clean he said there must be fuse where here and removed we then removed the fuse next to it we noticed the bass of this fuse has some dirt shows it is not been used before we but that fuse in that clean spot (40**) the car start right a way I think that was starter fuse ( what a coincidence) but truly I don't know how did this happened and how did it but any way am happy it start so I can finish what I did to convert it to rv (do you suggest or prefer I disconnect battery when I work in the car) thanks again for trying to help.

I have question how come the car reader did not motioned there is a fuse problems or missing and way mentioned only (ficm) this experience left me with doubts a bout such equipment to relay in there readings or help?
I also have little white smoke from the exhaust when I bought the car three months ago I checked the car with computer the result was injection no1 is closed and no 6 is 50% work I drove the car 100 miles after a filled the tanks and add a ( stop fuel injection cleaner) every thing was ok temperature and oil the last reading for the car did not mentioned any thing about engine or egr and egr valve what's your advice about white smoke?

Sorry again I fell like am writing stories thanks for your patient and help

Replaced engine. Used everything from blown engine except cam shaft. Engine cranks but will not fire. Where should I start first?

6.4 powerstroke. Code reading fuel injector pressure low

After replacing alternator and fully charging the two batteries does anyone know why the truck will not start