So the computer on my 96 ram 1500 5.9 is bad. My dad has a 99 ram 1500 5.9 it's the same flipping truck but according to my interchange program at work only a computer from a 96 will work. What's the difference? And will the 99 ecu actually work fine?

 

96-97 computer only. 98 and above are completely different

 

There is a part# on it, you need to use that when looking for new/used or rebuilt. You can get one for a 96 but it may be for a manual trans/5.2 so go by the # on yours.

 

1996 is an interesting year for the Dodge Ram truck. My early year 1996 Ram 2500 4x4 truck is an OBD1-OBD2 hybrid. It also has a R46RH transmission instead of the R46RE transmission. I've also replaced the computer (PCM) on my truck with a used PCM I found on eBay by matching the part number on the original PCM.

 

just curious does the pcm control the fuel pump relay? and I fount the ignition hot terminal but witch terminal goes down to the fuel pump? I wanna bypass the relay to see if fuel pump works

 

Terminal 30 is hot, and 87 goes to the pump. It's opposite to 30. You can see the pin out at the bottom of the relay, every pin is numbered.

 

so I popped a used ecu in it and it fired right up. truck sat for 9 months and when I got it to my shop showed 1/2 tank gas when I put the battery in even with old computer it instantly droped to dead empty. I assumed it was related to computer. installed new computer and still shows empty and fuel light on. it hs to have gas though cause it fires right up. would this issue be gauge cluster or fuel pump assembly?

 

More likely the sending unit in the fuel pump assembly. In a 96 the fuel gauge is "analog", straight resistance reading no PCM involvement. Note that if the wiring is broken the gauge will show empty as well. Reading at the sending unit should be close to zero ohms for full.

 

im assuming if the gauge thinks its empty than the low fuel light be on? im only asking cause I have a 95 eclipse that the fuel gauge was broken and the low fuel light was my indicator I needed gas cause it would come on when low but would go off when I filled the tank up

 

Different folks do it different ways. Even different year trucks do it different ways. On the 96, I do believe that the lite comes on when gauge voltage goes below a specific threshold.