Hella Pagid 355252141 Brake Pad Wear Sensor, Front

When your brake pads wear down to the limit, this is the part that tells you about it. The Hella Pagid 355252141 is a front disc brake pad wear sensor built for the small-car Mercedes-Benz platform and its Infiniti cousins. It has a simple job, but an important one. It rides along with the brake pad, and when the friction material wears thin enough, it completes the circuit that lights the wear warning on your dash. No guessing, no pulling wheels to eyeball pad thickness. The car tells you.

This one carries a 94 millimeter wiring harness and a two-pin female connector, and it's sold as a single sensor. That length and connector matter, because the same brake family uses different harness lengths front to rear. Get the 94mm front sensor when the car calls for it and the plug drops right into the factory connector. It's the genuine Hella Pagid part, catalog reference 8DK 355 252-141, replacing Mercedes OE A1695401617 along with the Infiniti and Nissan numbers 410685DN0A and 479105DA9A.

Fitment covers the Mercedes MFA small-car range: GLA250 and GLA45 AMG, CLA250 and CLA45 AMG, plus the A-Class and B-Class on the same architecture. Because Infiniti built the Q30 and QX30 on that Mercedes platform, this sensor crosses to those too. Model years run roughly from the mid-2010s forward. The catalog family is broad and Mercedes reused part-group numbers across a lot of chassis, so always verify against your VIN or match the old sensor's harness length and connector before you order. If your old sensor measures 94mm to the plug with a two-pin connector, you're in the right place.

Here's how it earns its keep. The sensor body sits in a pocket on the brake pad, with a loop of wire exposed near the friction surface. As the pad wears, the rotor eventually reaches that loop, breaks the circuit, and the brake wear lamp comes on. It's a one-time part by nature. Once it's triggered, the loop is damaged, so you replace the sensor every time you replace the pads it was riding with. Reusing a tripped sensor is the number one reason a wear light won't clear after a brake job.

Installation is straightforward for anyone comfortable doing their own pads. With the caliper off and the new pads going in, press the sensor into the pad's sensor pocket, route the harness along the factory clips so it doesn't rub the rotor or wheel, and click the connector into the chassis plug. Keep the wire away from moving suspension and heat. That's it. If the dash light doesn't clear after the job, check that the connector is fully seated and that you didn't pinch the harness.

Why genuine Hella Pagid? Pagid is an OE-level brake brand, and the wear sensor is one of those small parts where fit precision matters more than price. A sensor with the wrong connector or a harness that's an inch too short leaves you splicing wires or zip-tying a loop where it'll chafe through in a season. This one plugs in and routes the way the factory intended. For a part that protects your rotors from getting chewed up by worn-out pads, that's money well spent.

A few honest notes. This is the front-axle sensor for these platforms, and many of these cars run a sensor on one front corner only, so check how many yours actually has before buying a pair. It's a sensor, not a pad, so it doesn't come with brake pads, clips, or grease. And while the Mercedes and Infiniti fitment is well documented, the broader catalog lists hundreds of configurations, so a quick VIN check or a measurement of your old sensor is the surest way to confirm you've got the right one.