Two weeks ago my fuel gauge was working fine, went on vacation and just got back and now it does not work... When I got back the the Jeep (99 XJ) had a dead battery so I went to jump it and the fuel gauge registered half a tank which would have been correct.

After cranking and starting the engine the fuel gauge dropped to E and has been there ever since. I checked the plugs on the PCM and all looked good, the low fuel light is not on so I don't believe that it's a faulty fuel level sending unit. Not sure how to test it, does anyone know what ohm range the fuel level wire should be at? Maybe installing a standalone fuel gauge?

 

I tested the wire connecting to c26 on the PCM but I get a reading of 0 OHMS. I saw elsewhere on here that the pink wire (c27 on my jeep) is the fuel level signal and tested that and it came out to ~70 ohms. Not sure if on the model/year they were referring to. I added about a gallon of fuel but the reading did not change. If someone knows exactly what wire is the fuel level signal for now I can just attach a multimeter and read the ohm and estimate my fuel level from that. I am assuming it's my PCM gone bad again due to voltage spikes I had when I replaced it. Voltage spikes are fixed now but still trying to solve this issue.

 

For what it's worth mine has been doing this as well. I used BG44k and it worked again. I believe it can be the contacts on the fuel pump assembly that the floater arm makes contacts with to signal fuel level that get dirty. The detergent can clean them. BG44k can be hard to find but the chevron techron fuel system cleaner seems to be working as well. Not saying that's your issue but I thought I would throw it out there.