TECH TIP – ATE Magnetic Test Card Model: GLBATE760130
For some years now, modern vehicles feature active wheel sensors. These wheel sensors normally work together with magnetic sensor rings. The north and south magnetic poles (lying next to each other around the circumference of the ring) must always lie opposite the wheel sensor. If installed improperly, the system wheel sensor and magnetic sensor gear cannot supply a signal. In vehicle’s with this installation mistake, the ABS warning lamp will light up, but only after the vehicle is out on the road again.

The ATE Magnetic Test Card helps you avoid improperly installing wheel bearing replacements on vehicles equipped with Anti-lock Braking System (ABS) sensors.


  • Helps you avoid errors during wheel bearing installation which often results in customer comebacks and can also require additional resources to replace the recently installed but now newly damaged wheel bearings
  • Before pressing the wheel bearing in place, you can determine on which side of the wheel bearing the magnetic sensor ring is fitted (Figure C), so that you can properly arrange the side with the magnetic sensor ring to face the wheel sensor.
  • The Test Card will also be of good value for troubleshooting. If you discover during fault finding that the output signals of a sensor are obviously incorrect, but the sensor circuitry including the wheel sensor are okay, you can determine with the card whether one or more “teeth” (pairs of magnets) are missing (Figure D).
  • Never place a wheel bearing with magnetic sensor rings on a dirty workbench
  • Never place a permanent magnet anywhere near the magnetic sensor ring
  • Never insert sharp-edged or pointed tools in the bore of the wheel sensor as this can result in damage to the magnetic sensor ring
  • Make sure that the magnetic sensor ring and the wheel sensor are opposite each other
  • Fit the wheel bearings as instructed by the wheel bearing or vehicle manufacturer
  • Do not drive in the wheel bearing with a hammer and drift. Press in the wheel bearing using only tools intended for that purpose

Contributor: ACDelco Technical Assistance Centre
Questions? Please send us a note via our contact us. If you’d like to speak to one of our TAC agents, call the ACDelco Info-Line.