The key components involved in controlling the 4WD system include:
* Transfer Case: This is the primary mechanical component. It's located in the transmission area, under the vehicle. It physically engages and disengages the front drivetrain. It's not a module, but a crucial part of the 4WD system.
* Electronic Control Module (ECM) / Body Control Module (BCM): These modules (or possibly a single module handling both functions depending on the exact Avalanche trim) receive signals from various sensors (like the transfer case position sensor) and the driver (via the 4WD selector switch), then determine when to engage or disengage the 4WD system. These modules are usually located inside the vehicle, often under the dash or in the center console area.
* Various Sensors: Several sensors throughout the drivetrain send information to the ECM/BCM. These include things like transfer case position sensors and wheel speed sensors.
To troubleshoot a 4WD issue, a mechanic would need to diagnose the problem using diagnostic tools that can read codes from the ECM/BCM and check the operation of the transfer case and its associated sensors. There isn't one specific "4WD module" to locate.
