Where is the Body Control Module on a 2004 chevy malibu classic 2.2L for the clearance lights?

No there isn't. The Body Control Module (BCM) takes care of that. Check the grounds that are near the rear light, but you will need a good auto-electrician with a professional grade scan tool computer to check the BCM functions.

Here is your Fuses and Relays.

Fuse Box Diagram Chevrolet Malibu (2008-2012)

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Is the vehicle security light lit ? It could be a fuse or the starter relay , or even the ignition switch , or even the PNP - park neutral position switch . This is a complex electronic starting system , computer controlled . The ignition switch is a low voltage input to the the BCM - body control module . When the BCM receives this input to crank the engine a lot of complex commands are sent over the serial data network to the PCM to enegrize the starter relay , there by sending battery voltage to the S terminal on the starter solenoid . If your mechanic disconnected the battery it could have caused the radio to say locked , you need a code to enter into the radio to unlock it , may need to have the dealer hook up their factory scan tool to do that .
Your best bet , find a better automotive technician , not a mechanic.
Circuit Description (Key Start)
For ignition switch power modes refer to Body Control System Description and Operation in Computer/Integrating Systems. Once the ignition is placed in the Run/Crank position, the control circuit of the Run/Crank relay is grounded by the body control module (BCM). With the Run/Crank relay switch closed, battery positive voltage flows through it and on to the park/neutral position (PNP) switch. With the PNP switch in either the Park or Neutral position, battery positive voltage will flow to the starter relay coil supply voltage input terminal of the powertrain control module and the coil side of the starter relay. Placing the ignition in the START position sends a message to the powertrain control module (PCM) requesting engine start. If the PCM has determined that the transmission is in Park or Neutral and theft is not active, it will ground the control circuit of the starter relay. Battery positive voltage will then flow through the switch side of the starter relay to the S terminal of the starter solenoid, cranking the engine.

You take it to a qualified repair shop , unless you know about GMLAN serial data networks . U codes are network communication codes , problem with a module not talking or the data bus has a problem . GMLAN is general motors version of C.A.N. - controller area network . Watch this video .
https://www.youtube.com/watch?v=FqLDpHsxvf8

Then watch this. https://www.youtube.com/watch?v=VCgg89FeRHQ&t=1s

U0422 Invalid Data Received From Body Control Module
Body Control System Description and Operation Report a problem with this article
The body control system consists of the body control module (BCM), communications, and various input and outputs. Some inputs, outputs and messages require other modules to interact with the BCM. The BCM also has discrete input and output terminals to control the vehicle's body functions. The BCM is wired to the high speed GMLAN serial data bus, low speed GMLAN serial data bus and Multiple LIN buses and acts as a gateway between them.
Power Mode Master This vehicle body control module (BCM) functions as the power mode master (PMM). The ignition switch is a low current switch with multiple discrete ignition switch signals to the PMM for determining the power mode that will be sent over the serial data circuits to the other modules that need this information; the PMM will activate relays and other direct outputs of the PMM as needed. Refer toPower Mode Description and Operation for a complete description of power mode functions. Gateway The body control module (BCM) in this vehicle functions as a gateway or translator. The purpose of the gateway is to translate serial data messages between the GMLAN high speed bus and the GMLAN low speed bus for communication between the various modules. The gateway will interact with each network according to that network's transmission protocol.
All communication between the BCM and a scan tool is on the high speed GMLAN serial data circuits. A lost communication DTC typically is set in modules other than the module with a communication failure. Body Control The various body control module (BCM) input and output circuits are illustrated in the corresponding functional areas on the BCM electrical schematics. Refer to the Body Control System Schematics for more detailed information.

You may have a bad body control module.

usually cleaning the idle speed contrlol valve from carbon buildup, fixes idle surge and stalling. try soaking vave in throttle body cleaner or inyector cleaner.

Yes, because it is tied into the security system. If you can get the vehicle somewhere to do a code pull on the BCM, this may help get you closer to what is going on.

A big pain in the but* It's right under the throttle body, follow the throttle cables to where they attached to the intake, then look underneath to where the hose connects. You can change it without removing the throttle body assembly but it is probably easier to do so.

You would have to change the heater case to accept the electric motors splice in the wiring ,rplace the controls,and maybe the body control module I am not 100% sure on the body control module.

varies by location and damage, would need pictures ect, body shops give free estimates take to 3-4 and see what they say, anywhere from $1,000 up likely

Remote control door lock reciver an the BCM - body control module control the locks . The key switch is a electrical input to the BCM , the BCM controls the door lock actuators . Your best bet ,have it towed to the dealer .