Parking Brake Actuator

This procedure replaces the electric parking brake actuator on the rear brake caliper assembly of the 2023 Chevrolet Bolt EUV.

Warnings

Tools required

Parts

• Electric parking brake actuator (EPB motor) × 1 — Use OEM specification
• Actuator mounting bolts × 1 — Often included with actuator
• Brake fluid × 1 — ACDelco DOT 4

Fluids

• ACDelco DOT 4 Brake Fluid — 0.5 qt

Preparation

1. Park vehicle on level surface and engage parking brake (it will be released electronically in a later step)
2. Place wheel chocks at front wheels
3. Ensure ignition is OFF
4. Wait at least 2 minutes for high-voltage system to de-energize
5. Remove 12V auxiliary battery negative terminal to isolate electrical systems
6. Loosen rear wheel lug nuts while vehicle is on ground (do not remove)
7. Raise rear of vehicle with floor jack and support on manufacturer-approved jack stand points
8. Remove rear wheel on affected side
9. Extract small amount of brake fluid from master cylinder reservoir to prevent overflow during caliper piston retraction

Procedure

1. 1

   Reconnect battery and enter EPB service mode
   Temporarily reconnect the 12V negative battery terminal. Turn ignition to ON position (do not start - vehicle cannot start anyway as this is an EV). Connect scan tool to OBD-II port and navigate to Electric Parking Brake service functions. Select 'EPB Service Mode' or 'Retract EPB for Service' function. The scan tool will command the EPB actuator to fully retract and disable automatic parking brake application. Verify that the actuator has fully retracted before proceeding. Once confirmed, turn ignition OFF and disconnect 12V battery negative terminal again.
   ⚠️Do NOT attempt to remove actuator without entering service mode. The actuator motor maintains tension on the caliper piston and forced removal can damage components or cause injury.
2. 2

   Remove brake caliper from bracket
   Locate the two caliper slide pin bolts securing the caliper to the bracket. Apply penetrating oil if necessary and allow to soak. Using appropriate socket, remove both caliper slide pin bolts. Support the caliper assembly and carefully pivot it upward away from the rotor and bracket. Use wire or a bungee cord to support caliper from suspension - do NOT allow it to hang by the brake hose.
   ⚠Never allow brake caliper to hang unsupported by the flexible brake hose. This can cause internal hose damage leading to brake failure.
   Torque spec

   Caliper Slide Pin Bolts35 Nm (26 lb-ft)
3. 3

   Disconnect EPB actuator electrical connector
   Locate the electrical connector on the EPB actuator motor at the rear of the caliper. Press the release tab and carefully disconnect the wiring harness connector from the actuator. Inspect connector pins for corrosion or damage. Route the connector away from the work area.
   ⚠Handle electrical connector carefully to avoid bending pins. Corrosion or damaged pins can cause EPB malfunction.
4. 4

   Remove parking brake actuator from caliper
   The EPB actuator is secured to the rear of the brake caliper with two T30 Torx bolts. Using a T30 Torx bit, remove both actuator mounting bolts while supporting the actuator. Carefully withdraw the actuator from the caliper housing, ensuring the actuator drive mechanism disengages from the caliper piston spindle. Note the orientation and position of any O-rings or seals on the actuator interface.
   ⚠The actuator interfaces with the caliper piston via a spindle drive. Carefully align and disengage to prevent damage to the piston mechanism.
   Torque spec

   Mounting Bolts27 Nm (20 lb-ft)
5. 5

   Inspect caliper piston and spindle mechanism
   With actuator removed, inspect the caliper piston for damage, scoring, or corrosion. Verify the piston spindle mechanism rotates freely by hand. Check for brake fluid leaks around the piston boot. Clean any debris from the actuator mounting face on the caliper using brake cleaner. Inspect the actuator mounting bolt threads in the caliper for damage.
   ℹ️If piston spindle is seized, corroded, or damaged, the entire caliper assembly may require replacement. Do not attempt to force the mechanism.
6. 6

   Prepare new EPB actuator for installation
   Unpack new EPB actuator and verify it matches the original part. Inspect the new actuator drive mechanism to ensure it is in the fully retracted (service) position - the drive spindle should be minimally extended. If new O-rings or seals are provided, install them on the actuator according to manufacturer instructions. Apply a thin film of silicone brake grease to any O-ring seals to aid installation and prevent damage.
   ℹ️Some replacement actuators come pre-configured in service mode, others may need to be retracted using a scan tool after installation. Verify with part supplier.
7. 7

   Install new parking brake actuator
   Carefully align the new actuator with the caliper mounting surface, ensuring the actuator drive spindle properly engages with the caliper piston spindle mechanism. Apply medium-strength thread locker to the actuator mounting bolt threads. Install both T30 Torx mounting bolts and hand-tighten. Using a torque wrench with T30 Torx bit, tighten both mounting bolts to specification in a crossing pattern.
   ⚠Ensure proper engagement between actuator and piston spindle. Misalignment can cause actuator failure or inability to release parking brake.
   Torque spec

   Mounting Bolts27 Nm (20 lb-ft)
8. 8

   Reconnect EPB actuator electrical connector
   Route the wiring harness to the new actuator and firmly connect the electrical connector until it clicks into place. Gently tug on the connector to verify it is fully seated and locked. Ensure the wiring is routed clear of any rotating components, sharp edges, or heat sources.
9. 9

   Reinstall brake caliper to bracket
   Remove caliper support wire/bungee. Verify brake pads are properly positioned in the caliper bracket. Apply silicone brake grease to the caliper slide pin bolts as specified. Carefully position the caliper assembly over the rotor and align the slide pin bolt holes with the bracket. Install both caliper slide pin bolts and hand-tighten. Using a torque wrench, tighten both slide pin bolts to specification in the sequence recommended in the service manual.
   ⚠Ensure brake pads are correctly seated and rotor is centered between pads before tightening bolts.
   Torque spec

   Caliper Slide Pin Bolts35 Nm (26 lb-ft)
10. 10

    Reinstall wheel and lower vehicle
    Clean wheel mounting surface on hub. Install rear wheel and hand-tighten all lug nuts in a star pattern. Lower vehicle until tire just contacts ground (wheel cannot rotate). Using torque wrench, tighten wheel lug nuts to specification in a star pattern. Fully lower vehicle and remove jack stands and floor jack. Perform final lug nut torque verification.
    Torque spec

    Wheel Lug Nuts136 Nm (100 lb-ft)
11. 11

    Reconnect battery and exit EPB service mode
    Reconnect the 12V auxiliary battery negative terminal. Turn ignition to ON position. Connect scan tool and navigate to EPB service functions. Select 'Exit EPB Service Mode' or 'EPB Calibration' function. The scan tool will command the actuator through a calibration cycle - you may hear the actuator motor operating. Follow all on-screen prompts. Verify the scan tool indicates successful calibration and that no EPB fault codes are present.
    ⚠️EPB calibration is mandatory after actuator replacement. Failure to properly calibrate can result in parking brake not engaging or releasing, creating a serious safety hazard.
12. 12

    Verify brake fluid level
    Check brake fluid level in master cylinder reservoir. Top off with ACDelco DOT 4 brake fluid to the MAX line if necessary. Ensure reservoir cap is securely reinstalled. Wipe away any spilled fluid immediately.

Reassembly

1. Reassembly is covered in the procedural steps above, as this job requires specific sequencing during installation

Verification

• With vehicle in PARK and on level ground, attempt to engage parking brake using dashboard switch - verify indicator light illuminates and actuator operates
• Attempt to release parking brake using dashboard switch - verify indicator light extinguishes and actuator operates
• With vehicle running (ready mode), attempt to move vehicle with parking brake engaged - vehicle should not move
• Perform multiple engage/release cycles and verify smooth, consistent operation with no unusual noises
• Check for EPB fault codes using scan tool - verify none are present
• Visually inspect for any brake fluid leaks around caliper
• Test drive vehicle in safe area at low speed and verify normal brake operation and parking brake function on an incline
• After test drive, re-verify wheel lug nut torque and check for any signs of caliper interference or abnormal wear

Related trouble codes on this vehicle

Codes that commonly send this job to the bay — tap one for symptoms, causes, and diagnostic steps.

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