QUATTRO FRENI QF61F00158 WHEEL SPEED SENSOR (ABS)

The Quattro Freni QF61F00158 is a Rear ABS Wheel Speed Sensor for Ford, Mazda, and Volvo vehicles sharing the Ford C1 platform and Mazda BK/BL platform. It covers both rear-left and rear-right positions — the same physical sensor fits both sides of the rear axle. Primary OEM references: Mazda/Ford BP4K43711A / BP4K43711B, Volvo 30648986 / 30793635, and Ford numeric references 3M5T2B372BC/BD, 1225843, 1481190. The sensor is not interchangeable with front sensors — the rear sensor (BP4K43711A) and the front sensor (BP4K43701A) have different harness lengths and connector routing.

The sensor is mounted on the rear knuckle or trailing arm, with the sensing tip positioned against the magnetic encoder ring integrated into the inboard seal of the wheel bearing hub. As the rear wheel rotates, alternating magnetic poles on the encoder ring are detected by the Hall-effect element, generating a digital square-wave signal whose frequency is directly proportional to wheel speed.

The ABS module uses rear wheel speed data to detect impending lock-up during braking on the rear axle, and feeds the same data to ESP/ESC stability control (which detects oversteer and understeer by comparing front vs. rear wheel speed differences), Electronic Brake-force Distribution (EBD, which modulates rear brake bias), and Traction Control (which prevents rear wheelspin during acceleration on AWD/4WD variants). The encoder ring is integrated into the rear wheel bearing hub and cannot be replaced separately — a damaged ring requires full hub replacement.

ABS wheel speed sensors with integrated Hall-effect electronics are typically classified under HS 8543.70. Confirm the 10-digit subheading and applicable duty rates with your customs broker. Commercial invoice description: Automotive wheel speed sensor for anti-lock braking system.

Ford part numbers 3M5T2B372BC/BD have been superseded to BP4K43711A or later numbers in some catalogues — all are functionally equivalent for the applications listed. Verify fitment via VIN or original sensor part number before ordering. Ford Focus Electric (2012–2018) uses BP4K43711A — confirm by chassis number.

Difficulty: Easy to moderate — rear axle access. Estimated time: 25–45 minutes. The rear sensor harness routes along the rear trailing arm or axle — confirm the full routing path before removing the old harness clips.

1. 1
   Confirm fault position with a scanner. C0045 = left rear; C0050 = right rear. Use ForScan, Ford IDS, Volvo VIDA, Mazda M-MDS, or compatible Autel/Launch. Do not rely on a generic EOBD reader — ABS chassis codes require module-level access.
2. 2
   Raise and support the vehicle at the rear. Apply the parking brake, chock the front wheels, and support the rear corner on a rated axle stand. Remove the affected rear road wheel.
3. 3
   Inspect and clean the encoder ring before touching the sensor. With the wheel removed, the encoder ring integrated into the rear wheel bearing hub is accessible through the sensor bore or around the bearing inboard face. Use a non-magnetic brush or compressed air to remove any metallic debris, brake dust, or rust from the ring surface. If sub-code -5A was stored, this step alone may resolve the fault without sensor replacement.
4. 4
   Disconnect the 2-pin connector by tracing the harness along the trailing arm or axle housing to the connector clipped to the body or chassis. Press the locking tab and pull apart. Inspect connector pins for corrosion and clean with electrical contact cleaner if needed. Release all harness routing clips, noting their positions.
5. 5
   Remove the sensor mounting bolt (8 or 10 mm — verify on your vehicle). Apply penetrating oil if corroded and allow 10–15 minutes. Extract the old sensor by gentle rocking — do not pry against the knuckle. Clean the mounting bore with a cloth or wire brush. Verify the wheel bearing end play is minimal — excessive hub play indicates a worn bearing that requires replacement.
6. 6
   Install QF61F00158. Insert straight into the clean bore until seated flush. Torque the mounting bolt to 8–12 Nm. Do not overtighten — the plastic sensor housing will crack. Route the harness along the original path, securing all clips. Apply dielectric grease to the 2-pin connector before reconnecting.
7. 7
   Verify air gap with a feeler gauge if the vehicle has adjustment provisions. Rotate the hub by hand and confirm the gap between the sensor tip and encoder ring is consistent throughout rotation (0.5–2.5 mm typical). Significant gap variation indicates worn bearing play.
8. 8
   Refit the wheel and torque lug bolts/nuts to the vehicle specification. Lower the vehicle. Clear all ABS/ESP fault codes with a full-system scanner. Drive above 30 km/h to complete the ABS self-check. Confirm all warning lights have cleared.