The "4WD module" is likely referring to one of several components that could be causing 4WD problems. It could be:
* Transfer Case Actuator Motor: This is a common point of failure. It's an electric motor that shifts the transfer case between 2WD and 4WD. Replacing this often requires dropping the transfer case or at least significant disassembly to access it.
* Transfer Case Control Module (TCM): This is the electronic brain that controls the actuator motor. It receives signals from various sensors and sends instructions to the actuator. Replacing this usually involves locating it (often under the dash or near the transfer case), unplugging it, and plugging in the new module. However, simply swapping the module may not solve the underlying problem, and the new module may need programming.
* Range Sensor: This sensor tells the TCM which gear the transfer case is in. A faulty sensor can lead to incorrect 4WD operation.
* Other electrical components: Wiring harnesses, connectors, switches, etc., could also be the source of the issue.
General Steps (highly simplified and NOT a guide for DIY):
1. Diagnosis: Before replacing *anything*, you need a proper diagnosis to determine the actual faulty component. A simple visual inspection is insufficient. A mechanic will likely use a scan tool to check for diagnostic trouble codes (DTCs) and assess the operation of the 4WD system.
2. Disassembly (varies greatly depending on the failed component): Access to the component will require significant disassembly. This could involve removing parts of the undercarriage, potentially dropping the transfer case (a major job requiring specialized tools and knowledge), or removing interior components to reach the TCM.
3. Component Replacement: Once the faulty part is identified and access is gained, the old part is removed and the new part is installed. This requires attention to detail to ensure proper installation and alignment.
4. Reassembly: Carefully reassemble all components, ensuring everything is properly connected and secured.
5. Testing: After reassembly, the 4WD system must be thoroughly tested to verify that it is functioning correctly. This involves testing in different driving conditions and checking for any error codes.
Why You Shouldn't DIY This:
* Complexity: The 4WD system in a 2000 Chevy Blazer is intricate. Incorrect installation can cause significant damage to the vehicle, potentially leading to expensive repairs or even injury.
* Specialized Tools: Many specialized tools are required for this job, including potentially a transfer case drop-down tool.
* Safety: Working under a vehicle is inherently risky. Improper procedures can lead to serious injury.
* Programming: Some components might require programming using specialized tools.
Recommendation: Take your Blazer to a qualified mechanic specializing in 4x4 vehicles. They have the expertise, tools, and diagnostic equipment to properly diagnose and repair the 4WD system. The cost of professional repair will be far less than the potential costs of a DIY attempt gone wrong.
