Hello everybody

my XJR has 120K miles on it. my tach quit working, and it trips the transmission light and then the check engine light every time I drive it, and it will not go into 4th gear, the only codes it throws are general transmission fault and no engine speed signal, I pulled the transmission plug and cleaned, the wires appear to be fine, also my fuel gauge wobbles sometimes,
does anyone have any ideas

I suspect your instrument pack is faulty. There are services that test and repair them, or you could replace with a used one.