Bulletin BPI 07-16
Subject: Front Wheel Speed Sensor Corrosion
Vehicle Involved: 1999-2002 Chevrolet Silverado/GMC Sierra
2000-02 Chev Tahoe, Suburban/GMC Yukon, Yukon XL
2002 Chevrolet Avalanche
Condition: Corrosion may affect front wheel speed sensors causing false ABS
modulation at low speeds
Repair Procedure:
Vehicles listed above that are operated in corrosion-prone areas, where roadway
ice melting chemicals are commonly used in winter, may exhibit false ABS
modulation at speeds between 3.7 and 10 mph (6 and 16 km/h). This may be
caused by corrosion, between the front hub and bearing assembly, and the ABS
wheel speed sensor.
To check for this condition, inspect the wheel speed sensor where it is inserted
into the hub and bearing assembly. Begin by raising and supporting the vehicle
as necessary and removing the front wheels. Then, on each side:
1. Retract the caliper piston using a C-clamp. Caution: open the bleeder
screw when retracting the piston to avoid forcing contaminants into the
ABS hydraulic assembly.
2. Remove the entire caliper and bracket assembly as a unit by unbolting it
at the spindle. Hang the caliper assembly out of the way using
mechanic’s wire. Do not suspend the caliper by the brake hose, damage
to the hose may result.
3. Mark the relationship of the brake rotor to the hub, and remove the rotor.
4. Remove the bolt that attaches the wheel speed sensor to the bearing
assembly. (See Figure 1) Carefully remove the sensor by pulling it
straight out. Do not pry the sensor out, as the sensor body may break off
in the bore.
Affinia Group 4400 Prime Parkway McHenry, IL 60050 (815) 363-9000
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Figure 1
5. Inspect the mounting surface of the sensor. Use a straightedge to check
for flatness. If the surface is not flat, the sensor must be replaced. (See
#1 in Figure 2) The sensor can be reused if the surface is flat. (#2 in
Figure 2)
Figure 2
6. Temporarily plug the wheel speed sensor hole in the bearing hub to
prevent debris from entering the hub when it is cleaned.
7. Thoroughly clean the entire sensor mounting pad with a wire brush,
sandpaper, or Scotchbrite. All corrosion must be removed. Blow off all
loose debris with compressed air.
8. Coat the clean bare metal surface with rust-inhibiting paint, such as
Rustoleum. Use 2 light coats, allowing 5 to 10 minutes between coats.
Affinia Group 4400 Prime Parkway McHenry, IL 60050 (815) 363-9000
®Raybestos is a Registered Trademark licensed to Brake Parts Inc. by Raybestos Products Company
9. When the paint is dry to the touch, remove the plug from the hole in the
bearing hub. Coat the mounting surface and o-ring of the sensor with
silicone grease and insert it into the bearing hub. Install the mounting bolt
and torque it to 13 lb/ft (18 N-m).
10. Check the sensor for the proper signal: remove the connector from the
wheel speed sensor and connect a digital voltmeter across the terminals.
Rotate the hub at a rate of about one revolution per second. The
minimum reading should be 350 mV AC. If the reading is less, the wheel
speed sensor must be replaced. If the sensor is replaced, repeat this step
after installing the new one.
11. Clean the hub flange and rotor mounting surfaces of any rust, foreign
material, or nicks. Reinstall the rotor, matching the indexing marks made
on disassembly.
12. Install the caliper and bracket assembly. Clean the threads of the
mounting bolts and apply threadlocker before installing. Torque the bolts
to the following specification:
1500 Series vehicles: 129 lb/ft (175 N-m)
2500 Series vehicles: 221 lb/ft (221 N-m)
13. After completing the above procedure for both sides, install the wheels
and torque the lug nuts to 140 lb/ft (190 N-m).
14. Depressing the pedal no more than 2/3 travel, slowly depress and release
the brake pedal to seat the caliper pistons and pads before moving the
vehicle.
Affinia Group 4400 Prime Parkway McHenry, IL 60050 (815) 363-9000
®Raybestos is a Registered Trademark licensed to Brake Parts Inc. by Raybestos Products Company