* Wiring Issues: This is the most likely culprit. A break in the wire between the brake switch and the light(s), a short to ground, or a corroded connection anywhere along the path will prevent the light from working. Inspect the wiring harness carefully, looking for frayed wires, broken insulation, or corrosion, particularly near the brake pedal and the tail light assemblies.
* Bad Brake Light Bulb(s): Even with a new fuse and switch, a burned-out bulb is a simple possibility. Test the bulbs with a multimeter or by swapping them with known good bulbs from other working lights (e.g., turn signals).
* Bad Ground Connection: A poor ground connection at the tail light assembly or the chassis can interrupt the circuit. Check the ground wires for corrosion or loose connections. Cleaning the ground connection points often solves this issue.
* Faulty Tail Light Assembly: The problem could be within the tail light assembly itself. The socket might be faulty, or there could be an internal short. Try swapping the tail light assembly with a known good one if possible.
* Incorrect Wiring: It's less likely, but possible that the wiring was incorrectly reconnected during the switch replacement. Double-check the wiring diagram to ensure everything is properly connected.
* Relay (if applicable): Some vehicles, though less common in 1991, might use a relay in the brake light circuit. A faulty relay could also be the problem. Check your vehicle's wiring diagram to determine if a relay is used.
* Centralized lighting control module (unlikely, but possible): Some cars utilize a control module, although less common in Corollas of that year. A faulty module might be the reason, although it's usually accompanied by other lighting issues.
Troubleshooting Steps:
1. Check the bulbs: This is the easiest and quickest thing to do first.
2. Visually inspect the wiring: Look for obvious breaks, corrosion, or damage.
3. Test the brake light switch: Even with a new switch, it's possible it's faulty. You can test its continuity with a multimeter when the brake pedal is pressed.
4. Check the ground connection(s): Clean and tighten ground connections at the tail lights and chassis.
5. Use a multimeter to trace the circuit: This is the most effective way to pinpoint the exact location of the fault. You'll need a wiring diagram and a basic understanding of automotive electrical systems.
If you're not comfortable working with car electrical systems, it's best to take your Corolla to a qualified mechanic. Improperly diagnosing and fixing electrical issues can lead to further damage.
