What would cause a loud roaring in the back seat of my 2001 Monte Carlo as I am driving?

Did you check fuses and relays first? Diagnose first, then repair. A new motor comes after you connect 12 volts to the old one and see if it works.

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Fuse Box Diagram Chevrolet Monte Carlo (2000-2005)

https://fuse-box.info > chevrolet > chevrolet-monte-carl...
2000, 2001, 2002, 2003 - Here you will find fuse box diagrams of Chevrolet Monte Carlo 2000, 2001, 2002, 2003, 2004 and 2005, get information about the ...

Does it have a clutch fan or electric fan ? Clutch fans make a loud roaring noise when going bad.

A common problem with this generation of MC's is the ISS, or intermediate steering shaft. The shaft turns with the wheels and does exactly what you describe. If it isn't too far gone, a repair shop can do a lube job on it and some more parts on your front end to fix the symptom. If it is too far gone, you will need a new ISS.

There are other front end problems (power steering, wheel hubs, axles, brake rotors, etc.) that will cause similar noises and symptoms. If you aren't highly skilled and mechanically inclined, it is much better to just take the car into a repair shop for a diagnosis and/or estimate than to throw parts and labor at the general area. If somebody makes a bad judgement or two, the cost of replacing parts that do not eliminate the root cause will quickly add up to more than the cost of a proper repair. Not to mention the time involved.

run the fault codes again and fix all of what is suggested in the causes.

torck converter

I belive the ECM is under the dash above emergency brake . The PCM is under the seat and the BCM is under the air filter box under the hood.

Check your belts for dried fluid on them because this happened to my '95 Monte, the radiator pipes leaked onto the belts then dried and caused the squeaking.

On these websites you fond fuse box diagram, description for Chevrolet Monte Carlo (2001)

Chevrolet Monte Carlo 2001 2003 fuse box diagram Auto Genius

http://www.carknowledge.info/chevrolet-monte-carlo-2001-2003-fuse-box-diagram

jack up one side and feel for movement or rumble to confirm bearings are f.......

just rotate the belt in a clock wise direction