Replacing all brake pads simultaneously isn’t necessary unless they’re all worn down. Only pads on the same axle require replacement at the same time. There’s no advantage to replacing all pads at once since replacing front and rear pads involves separate tasks (besides possibly lifting the car). Doing them all at once takes the same amount of time as replacing them individually and summing the time spent.
Considering that rotor replacement often accompanies every second or third brake pad change, replacing all pads together wastes pad and rotor material prematurely. If the front pads triggered the warning, replacing all pads wastes rear pad, rotor, and parking brake shoe material—unnecessary replacements simply for the sake of simultaneous service.
To determine which pads triggered the warning, visually inspect pad wear. If inconclusive due to caliper obstruction, check each sensor’s continuity with a multimeter. Alternatively, use a known-good brake pad sensor, connect it to each wheel’s wear sensor socket, and observe if the warning disappears. (This method might not work with multiple worn sensors, or at least not with a single replacement sensor).
Accessing wear sensor connectors is possible without wheel removal, provided the car can be lifted. This allows quick and easy identification of the faulty sensor. This process can be aided by using a VCDS (Vag-Com Diagnostic System) tool to pinpoint the specific wheel triggering the pad wear warning light. The VCDS system can read error codes from the car’s computer, identifying the exact location of the fault, saving time and potentially unnecessary repairs. Using VCDS in conjunction with a visual inspection can provide a comprehensive diagnosis of brake pad wear.
