* Parking Brake Cable Adjustment: This is the most common cause. The cables might be too tight, causing them to partially engage even when the lever isn't pulled. This needs adjustment or repair.
* Brake System Malfunction: A problem with your hydraulic braking system could trigger the emergency brake system as a safety measure. This could include:
* Low Brake Fluid: Check your brake fluid level immediately. Low fluid suggests a leak somewhere in the system.
* Faulty Brake Master Cylinder: The master cylinder is the heart of your braking system. A failing master cylinder can lead to erratic brake behavior.
* Faulty Wheel Cylinder or Caliper: A problem with one or more wheel cylinders (rear brakes) or calipers (front or rear brakes) can cause the emergency brake to engage or mimic its effects. This could involve sticking pistons, leaks, or internal damage.
* ABS Module Issues (Less Likely but Possible): The anti-lock braking system (ABS) is connected to the braking system, and a malfunction within the ABS module could interfere with brake function and possibly trigger the emergency brake.
* Brake Light Switch: A faulty brake light switch can sometimes send incorrect signals to the system, potentially causing the emergency brake to engage or mimic its symptoms.
* Wiring Issues: Damaged or shorted wires in the braking system's wiring harness can cause erratic behavior, including unintended emergency brake activation. This is often caused by corrosion or rodent damage.
* Emergency Brake Lever/Mechanism: Although less likely while driving, there's a small chance the lever itself or a linkage component is sticking or malfunctioning.
What to do immediately:
1. Pull over safely to the side of the road. This is crucial for your safety and the safety of others.
2. Turn off the engine.
3. Check your brake fluid level. Low fluid is a serious indicator of a leak.
4. Inspect the emergency brake lever. Make sure it's completely released.
5. Do NOT attempt to drive further. Driving with a partially engaged emergency brake can severely damage your brake system, overheat your brakes, and cause a loss of control.
What to do next:
Have your vehicle towed to a qualified mechanic. Describing the problem accurately (emergency brake engaging while driving) will help them diagnose the issue efficiently. Ignoring the problem could lead to a dangerous situation.
