1. Fuses and Relays: This is the first and cheapest thing to check. The Impala SS's cooling fan system uses fuses and relays to control power. Check the fuse box (usually under the hood and/or inside the cabin) for blown fuses related to the cooling fans. Also, inspect the relays; they can sometimes fail internally even if the fuse is intact. Replacing these is inexpensive.
2. Fan Motor: If the fuses and relays are fine, the problem could be the fan motor itself. This is more expensive to replace and requires more mechanical skill. You might be able to test the motor directly with power (but be cautious!), but often it's easier to just replace it if the other steps are ruled out.
3. Fan Control Module (PCM/ECM): The Powertrain Control Module (PCM) or Engine Control Module (ECM) controls the fan's operation. A faulty module could prevent the fan from activating. This is the most expensive and complex part to replace and generally only considered after exhaustive testing of the simpler components. Often a diagnostic scan tool is needed to check the PCM's output for the fan.
4. Wiring and Connections: Inspect all the wiring leading to the fan motor, relays, and fuse box for any damage, corrosion, or loose connections. A simple broken wire can prevent the fan from working.
5. Temperature Sensor(s): The cooling system relies on temperature sensors to tell the PCM when to activate the fan. A faulty sensor might prevent the fan from turning on, even when overheating. Replacing this is relatively inexpensive but diagnosing the faulty sensor would involve testing its output.
In short: Start with the fuses and relays. If those are good, then move on to inspecting wiring and connections. Only after ruling out these simpler and cheaper options should you consider replacing the fan motor or the PCM/ECM. A diagnostic scan tool can be extremely helpful in pinpointing the exact cause.
