* Short Circuit: A short circuit in the wiring harness is the most probable cause. The brake light circuit is somehow interacting with the hazard light circuit due to a faulty wire, connector, or ground. This short could be anywhere between the brake pedal switch, the fuse box, and the hazard light switch.
* Faulty Brake Light Switch: While a faulty brake light switch will usually just prevent the brake lights from working, a severe malfunction *could* cause a short that affects other circuits, including the hazard lights.
* Faulty Hazard Light Switch: Less likely, but a malfunctioning hazard light switch itself could be causing this crosstalk.
* Faulty Body Control Module (BCM): The BCM manages many electrical functions in the vehicle. A fault within the BCM could cause incorrect signals to be sent to both the brake lights and hazard lights. This is less likely than a wiring issue but possible.
* Incorrect Wiring Repair: If you've recently had any electrical work done, particularly around the brake lights or hazard lights, it's possible a wire was incorrectly connected.
What to do:
1. Safety First: This is a serious electrical issue. Driving with this problem could lead to further damage or even a fire. Avoid driving the truck until the problem is fixed.
2. Check Fuses: Begin by checking the fuses related to the brake lights and hazard lights in the fuse box. Look for blown fuses. However, a blown fuse is a *symptom*, not the root cause; replacing a blown fuse without fixing the underlying short will likely just result in another blown fuse.
3. Visual Inspection: Carefully inspect the wiring harness in the area of the brake pedal, brake light switch, and hazard light switch. Look for any damaged, frayed, or melted wires. Pay special attention to any areas where wires might be rubbing against metal parts.
4. Professional Diagnosis: Given the complexity of the problem, taking your S-10 to a qualified mechanic or auto electrician is highly recommended. They have the tools and expertise to diagnose and repair the short circuit or faulty component causing this issue. Describing the problem clearly will help them expedite the diagnosis.
Ignoring this issue is dangerous. Get it checked out as soon as possible.
