jeepdiy

My fuel gauge needle varies between 7/8 and 5/8 tank level however much gas I have in my tank, and even if it's close to empty. I've had this problem even before replacing the fuel pump and level sending unit. Dealer tells me it is the PCM. Is the sending unit sending level signal to the PCM or direct to instrument cluster? Is there a schematic I can pull up somewhere?

jeepdiy

For those who may have same issue/question, the sending unit fuel level sensor signal does connect to the PCM direct, and not to instrument cluster fuel gauge. PCM then sends signal to fuel gauge in instrument cluster over what Jeep calls the PCI bus. Not sure if this would be the same as PCI bus in PC nomenclature. Anybody has any ideas on this PCI bus protocol? The fuel level sensor seems to be sending a reasonable voltage signal to PCM. PCM is sending what appears to be correct signals to all instrument panel gauges except the fuel gauge. I may have to replace the PCM after all, but would like to make sure.