I have a 2001 Jeep Cherokee and all the needles on the gauges start flopping up and down and in the odometer space it said NO BUS what does this mean

It means the dash cluster has lost communication with the ECU.

I am not a car person so can you explain a little more about what this ECU is

An engine control unit (ECU), also commonly called an engine control module (ECM), is a type of electronic control unit that controls a series of actuators on an internal combustion engine to ensure optimal engine performance. If the gauge fluctuation occurs it's usually a voltage drop from a weak or intermittent connection. Check your connections from gauges (cluster) to right behind it and the ground wire(s) to dashboard. Hopefully this is the problem. Good Luck.

we have done all the checking and now when the head lights are off the turn singles wont work, would this be caused if the headlight switch is bad

I'm with the same problem, I have a JEEP XJ 2.5 TD 33 "12.5, I live in Brazil. I'm immobilized due to the" NO BUSS "sign. I tried everything already. Now I'm going to try to recode the module. I beg for information. My module is German BOSH, my mobilizer is Mexican and the electric module is Canada. I'm desperate and without a car so far. HELP antonioecocerrado@gmail.com watts app +55 062 98160 7708

I had this and solved it. This was about 5 years ago, so I hope I remember. NO BUSS symptom. Under the dash there is a fairly large multiple-wire connector that connects all the dash electrics to the car. Disconnect it and clean it VERY thoroughly using Contact Cleaner. Some say apply dielectric grease on the contacts. I did not do that. Re-connect and ti should be ok. Mine was.