That would be my guess. In the world of computing a bus is something that allows data to be communicated between different pieces of hardware.
That said, it might me something completely off-the-wall because engineers love to screw with people. I recently stumbled upon the meaning of the infamous printer error "PC LOAD LETTER" and the meaning is ridiculous! "PC" stands for "paper cassette" instead of "personal computer" like every normal person would assume, and "LETTER" refers to 8.5"x11" letter-sized. What the hell is a paper cassette anyway? Has anyone in the real world ever referred to a paper tray as a paper cassette? Why didn't they make the error say "LOAD PAPER"!
There's actually eight variants of that message in US printers. PC, LC, MP, and MF, LOAD LEGAL, and LOAD LETTER (other countries refer to their standard paper sizes). It was an attempt by HP to standardize error messages, and this was from before "Personal Computers" were common. Computers were strictly office equipment. It was also a time where memory was very expensive so things were abbreviated wherever possible. Today's printers and all-in-ones tell you exactly what they want in plain english (most even SHOW you in pictures).
PC = Paper Cassette (Top tray), LC = Lower Cassette (bottom tray), MP = MultiPurpose Tray (can be assigned to either a cassette or tray, but must have adjustable paper guides), and MF = Manual Feeder (the single sheet feeder on the front, usually used for envelopes or label sheets).
But anyway back to the OP, you will want to go through and check all of your ground points, check all of your fuses, and check all of the PCM connections. Pull the plugs out and make sure there is no corrosion. Make sure the wires have not been chewed by animals.
Also check the Crankshaft Position Sensor (passenger side, bottom rear of the engine, accessible through the wheel well).. There is a known issue where this sensor shorts the 5V lead to ground, which puts the computer into protection (read: sits there like a brick) mode. Unplug the sensor, then disconnect the negative battery lead for 1 minute, then reconnect and see if the nO bUS message goes away. There are actually four separate sensors that could cause this problem (they are all connected to the same +5v lead), but the crank position sensor is the usual culprit. The others are Cam position sensor, MAP sensor, and Throttle Position sensor.
If it turns out you do need a new PCM, be VERY careful buying one from a junkyard. You have to match year, model, engine size, and features like security and transmission, then it still needs to be flashed at the dealer with your VIN and mileage, and most junkyards offer no returns on electrical parts so if its bad or wrong, you're stuck with it. Better off buying a new one.