When is it required to remove the pressure modulator fuse in an anti-lock brake system?

In an anti-lock brake system (ABS), the pressure modulator plays a critical role in controlling brake pressure to prevent wheel lock-up during braking. When a "space-saver" spare tire is used, the vehicle's dynamics can change significantly. These spare tires are typically smaller in diameter than standard tires, which can create an imbalance in the system if the anti-lock brake system remains active.

Removing the pressure modulator fuse in this situation is important because leaving it connected while using a space-saver tire can lead to incorrect readings from the ABS sensors, which may result in erratic brake behavior. The ABS system relies on the uniformity of tire sizes for optimal performance, and having one smaller tire can interfere with the system's ability to detect wheel speed accurately.

This action ensures that the vehicle remains safe to operate, as it disables the ABS function until a regular tire can be put back on. The other scenarios—worn brake pads, changing brake fluid, or bleeding air from the lines—do not require the fuse to be removed and can be performed without needing to disable the ABS system.