* Wiring: Check the wiring harness leading to and from the horn relay. Look for broken, corroded, or loose wires. Pay close attention to the connections at the relay itself, the horn button, the horn(s), and any connectors along the wiring path. A visual inspection might not be enough; you might need a multimeter to test for continuity.
* Horn(s): The horn itself could be faulty. Test the horn directly with power (carefully, using a multimeter to verify power and ground, and using appropriate safety measures). If it doesn't work with direct power, the horn is bad.
* Horn Button/Steering Wheel Switch: The switch in your steering wheel that activates the horn might be broken or worn out. This is often a common point of failure. It's possible to test continuity through the switch with a multimeter.
* Fuse: Even though you changed the relay, there might be a blown fuse in the circuit protecting the horn. Check your owner's manual to locate the appropriate fuse and test it.
* Ground Connection: A poor ground connection can prevent the horn circuit from completing. Inspect the ground connection points associated with the horn and the horn relay. Ensure a clean and secure connection.
* Body Control Module (BCM): In some cases, the BCM could be sending a faulty signal to the horn relay, even if the relay itself is working. This is less likely but possible.
How to troubleshoot:
1. Start with the simplest: Check the fuse first.
2. Visual inspection: Carefully examine all wiring for damage.
3. Continuity testing: Use a multimeter to check for continuity in the wiring from the horn button, through the relay, and to the horn itself.
4. Direct power test: Test the horn directly with power to rule out a faulty horn.
5. Ground connection: Inspect all ground connections.
If you are not comfortable working with car electronics, it's best to take your Impala to a qualified mechanic for diagnosis and repair. Improperly working with car electrical systems can be dangerous.
