Here's a breakdown of where to start troubleshooting, prioritizing safety:
1. Safety First:
* Do not attempt to drive the truck. The inability to shift out of park is a critical safety issue, and driving with a potentially shorted braking system is extremely dangerous.
* Have the vehicle towed to a safe location. Don't risk further damage or injury.
2. Initial Checks:
* Check the fuse itself: Make sure the replacement fuse is the correct amperage. If it blows immediately upon replacement, there's a definite short circuit. Don't keep replacing the fuse; that's just masking the problem.
* Inspect the wiring: Visually examine all wiring related to the ABS system and brake light switch. Look for any chafing, fraying, melted insulation, or signs of water damage, especially around the brake pedal assembly and under the dash near the fuse box. Pay close attention to the wiring harness near the ABS module.
* Brake light switch: This is a common culprit. It's relatively inexpensive and easy to replace, but it's crucial to ensure the switch isn't shorted before replacement. A faulty switch *can* cause the symptoms you describe.
3. Potential Causes (in order of likelihood):
* Short circuit in the wiring harness: This is the most probable cause given the symptoms. A short can occur anywhere in the wiring leading to or from the ABS module, brake light switch, or other related components. Tracing the wiring harness may require significant time and expertise.
* Faulty ABS module: The ABS module itself could be internally shorted. This is a more expensive repair as the module usually needs replacement.
* Brake light switch (again): A shorted brake light switch is likely to trigger the brake light, ABS light and prevent shifting out of park.
* Transmission range sensor: While less likely given your other symptoms, a faulty transmission range sensor can prevent shifting out of park. However, it usually doesn't involve ABS and brake lights.
* Other related sensors (speed sensors, etc.): A faulty sensor in the braking system *could* contribute to these symptoms, though less likely than a short circuit.
4. Troubleshooting Steps (After Towing):
* Systematic Wiring Inspection: With the truck safely secured, use a multimeter to carefully trace the wiring from the fuse to the various components (ABS module, brake light switch, etc.) to pinpoint the short. This may require a wiring diagram specific to your 1997 Ford F-150.
* Professional Diagnosis: This is strongly recommended. An automotive mechanic with experience in electrical systems and braking systems will have the proper tools and knowledge to diagnose and repair the problem safely and efficiently. They'll be able to test the various components and identify the source of the short circuit.
In summary: Don't try to fix this yourself unless you have extensive electrical diagnostic experience. The safety risk is too high. Get the truck towed and seek professional help. Explain the symptoms clearly to the mechanic – the inability to shift out of park is critical information.
