Electronic Parking Brake Motor

Replace the electronic parking brake motor (actuator) on the rear brake caliper to restore parking brake function.

Warnings

Tools required

Parts

• Electronic parking brake motor/actuator × 1 — ACDelco 84664620 or equivalent
• Brake fluid × 1 — DOT 4
• Brake caliper mounting hardware kit × 1 — Use OEM specification

Fluids

• ACDelco DOT 4 Brake Fluid — 0.25 qt

Preparation

1. Verify that you have a scan tool capable of retracting and calibrating the electronic parking brake system before beginning
2. Park vehicle on level, solid ground and place wheel chocks in front of both front wheels
3. Connect OBD-II scan tool and verify communication with EPB control module
4. Turn ignition to ON position (engine off) and release electronic parking brake using dashboard switch
5. Using scan tool, enter EPB service mode and command actuators to fully retract position
6. Disconnect negative battery cable and wait 2 minutes for system capacitors to discharge
7. Raise rear of vehicle and support securely on jack stands at frame rails, not rear axle
8. Remove rear wheel on side requiring service using 22mm socket
9. Extract small amount of brake fluid from master cylinder reservoir using turkey baster to prevent overflow during caliper compression

Procedure

1. 1

   Access the EPB motor
   Inspect the rear brake caliper and locate the electronic parking brake motor assembly on the inboard side of the caliper. Remove the protective dust cap if equipped. Clean the area around the motor mounting bolts with brake cleaner and wire brush to prevent contamination.
2. 2

   Disconnect EPB electrical connector
   Locate the EPB motor electrical connector. Press the locking tab and carefully disconnect the wiring harness from the motor. Inspect connector pins for corrosion or damage. Note the routing of the wire harness for reinstallation.
   ⚠Do not pull on wires; press release tab firmly and pull connector body only.
3. 3

   Remove caliper slide pin bolts
   Remove the upper and lower caliper slide pin bolts using an 18mm wrench or socket. Support the caliper body to prevent it from falling or stressing the brake hose. The caliper does not need to be fully removed unless the motor cannot be accessed while installed.
   ⚠Do not let caliper hang by brake hose. Support caliper with wire or bungee cord if pivoting away from mounting bracket.
   Torque spec

   Caliper Slide Pin Bolts35 Nm (26 lb-ft)
4. 4

   Remove EPB motor mounting bolts
   Locate the two EPB motor mounting bolts on the rear of the caliper body (typically M8 or M10 bolts). Remove both mounting bolts completely using appropriate socket. Note the position and orientation of the motor for installation of replacement unit.
   ⚠️Motor may be under residual spring tension. Remove slowly and keep fingers clear of piston mechanism area.
   Torque spec

   Mounting Bolts34 Nm (25 lb-ft)
5. 5

   Remove EPB motor from caliper
   Carefully pull the EPB motor straight out from the caliper body. The motor gear engages with the caliper piston screw mechanism. You may need to rotate the motor slightly while pulling to disengage. Inspect the motor mounting surface on the caliper for damage, corrosion, or debris.
6. 6

   Inspect and clean caliper piston mechanism
   With the motor removed, inspect the caliper piston screw drive mechanism for damage, corrosion, or contamination. Clean the mounting surface and piston mechanism with brake cleaner. Verify that the piston screw mechanism rotates freely by hand. If binding is present, the entire caliper may need replacement.
   ⚠Do not use petroleum-based lubricants on brake components. Use only approved silicone brake grease on specified areas.
7. 7

   Prepare new EPB motor
   Remove new EPB motor from packaging and verify correct part number matches original. Inspect the motor drive gear for any shipping damage. Apply a thin coating of silicone brake grease to the O-ring seal on the motor body if equipped. Do not apply grease to the gear mechanism.
8. 8

   Install new EPB motor
   Align the new EPB motor gear with the caliper piston screw mechanism. Insert the motor straight into the caliper body, rotating slightly if necessary to mesh the gears. Ensure the motor seats fully against the caliper mounting surface before proceeding.
   ⚠Do not force motor installation. If resistance is encountered, remove and verify gear alignment.
9. 9

   Install EPB motor mounting bolts
   Install both EPB motor mounting bolts and hand-tighten. Verify motor is properly seated and aligned before final tightening. Torque mounting bolts to specification in a cross pattern to ensure even seating.
   Torque spec

   Mounting Bolts34 Nm (25 lb-ft)
10. 10

    Reconnect electrical connector
    Route the EPB wiring harness in the original path, ensuring it will not contact moving suspension components or brake rotor. Connect the electrical connector to the new motor until the locking tab clicks into place. Gently tug on connector to verify secure connection.
11. 11

    Reinstall brake caliper
    If caliper was pivoted or removed, clean the caliper slide pins with brake cleaner and inspect the rubber boots for tears. Apply fresh silicone brake grease to the slide pins. Position caliper over brake pads and bracket, then install both slide pin bolts. Torque to specification.
    Torque spec

    Caliper Slide Pin Bolts35 Nm (26 lb-ft)
12. 12

    Reconnect battery and perform initial calibration
    Reconnect negative battery cable. Turn ignition to ON position without starting engine. Using scan tool, exit EPB service mode if still active, then perform EPB motor initialization/calibration procedure. This process typically takes 20-45 seconds per side and you will hear the motor operating.
    ⚠Do not interrupt calibration procedure once started. Ensure battery voltage remains above 12V throughout process.
13. 13

    Test EPB function
    Using the scan tool, command the EPB to apply and release several times. Verify smooth operation with no unusual noises. Use the dashboard EPB switch to apply and release parking brake. Confirm dashboard warning light operates correctly and motor engages smoothly.
14. 14

    Reinstall wheel and perform final checks
    Reinstall rear wheel and hand-tighten lug nuts in star pattern. Lower vehicle until tire just touches ground to prevent wheel rotation. Torque lug nuts to specification in proper star pattern sequence. Fully lower vehicle and remove jack stands.
    Torque spec

    Wheel Lug Nuts190 Nm (140 lb-ft)

Reassembly

1. Top off brake fluid reservoir to MAX line with DOT 4 brake fluid if level dropped during service
2. Clear any diagnostic trouble codes from EPB system using scan tool
3. If both rear EPB motors were replaced, ensure both sides have been calibrated individually
4. Verify all tools and parts have been removed from wheel well area

Verification

• With vehicle on level ground and engine running, apply EPB using dashboard switch - verify both rear wheels lock and cannot be rotated by hand
• Release EPB and verify both rear wheels rotate freely with no dragging
• Apply EPB at least 5 times and verify consistent engagement with no grinding, clicking, or unusual motor sounds
• Check for EPB-related diagnostic trouble codes using scan tool - there should be none present
• Test drive vehicle at low speed (5-10 mph in safe area) and apply EPB to verify it brings vehicle to controlled stop
• Park on incline (if available) and verify EPB holds vehicle stationary in both forward and reverse orientations
• Verify EPB dashboard indicator light illuminates when applied and extinguishes when released
• Recheck brake fluid level after test drive - top off if necessary

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