There’s No Stopping the Electric Parking Brake
The advent of electronic parking brake (EPB) systems offers advanced technology but can pose challenges for the service technician. This article explains the current systems and provides insight regarding understanding and troubleshooting these non-mechanical approaches.
The use of an electric parking brake (EPB) system is not new. It’s been on some vehicles since the late 1990s, but there seems to be a surge to move to the EPB system on many new models.
One major worldwide brake supplier has now produced over sixty million caliper-integrated EPB units (the parking brake motor is part of the caliper) and has moved on to their fifth generation of EPB designed products. It is even showing up on popular pickup truck models.
EPB eliminates the mechanical connection between the operator and the parking brakes; it’s now operated by wire. The system uses an electric switch to activate and deactivate the parking brakes.
The EPB system requires an electronic control unit (ECU).
Some earlier versions had a stand-alone ECU, but most of today’s versions of the EPB system are almost always integrated into the vehicle’s controller area network (CAN) architecture. This provides the EPB system the ability to use and share information from the other modules on board for a multitude of functions.
The reasons behind EPB and the two common designs
There are two common designs used in the EPB system: the cable puller system and the caliper-integrated system. It is important to note that neither system will function if there is no vehicle power.
The cable puller design motorizes the traditional handbrake or parking brake pedal function by using a bidirectional motor. This bidirectional motor supplies the pulling force to the brake cables that run to either the rear calipers or the parking brake shoes (a drum-in-hat rotor style).
The advantage of this style of EPB system is that it lends itself to be an add-on solution, using some existing parts. Existing cable style brake calipers or parking brake shoes can easily be adapted to use the cable puller EPB.
The CAN connected cable puller EPB controller/actuator can be tucked somewhere under the car or even in the trunk. Many of the first designed cable puller units provided some form of manual release mechanism in the event of a motor failure. Some manufacturers provided access ports and in some cases tools to release the cables.
For example, Range Rover had a special cable release under the center console. The cable puller design has been popular and is still being used, but the caliper-integrated design has gained popularity and its simplicity will likely make it the favorite.
The caliper-integrated design incorporates a bidirectional electric motor on each caliper. This electric motor mechanically forces the caliper piston out to provide the necessary clamping force on the rotor. Most systems will use a gear reduction drive to provide the needed force with a small electric motor.
There are several advantages to the caliper- integrated EPB design setup. It eliminates the need for brake cables and the hardware and packaging they require. Another advantage is that the vehicle manufacturing process is streamlined requiring only one hydraulic and one electrical connection on each rear-brake assembly. An added advantage is weight reduction.
One manufacturer claims it saves as much as 16 pounds on a full-size SUV/pickup. Reducing vehicle weight, reduced emissions and increasing fuel economy is a common theme in today’s automotive world.
The will be CAN networked, allowing integration into other on-board systems. The caliper-integrated EPB system is commonly used on Volvo, VW, Audi, Ford F-150, Honda and many others.
Space saving is another advantage to the EPB system. The area that was devoted to a pedal assembly or a parking brake handle unit in the traditional hump area, foot well, and center consoles, can now be used for other things.
Some manufacturers claim there’s increased occupant safety by the removal of the handle or pedal assemblies during a collision. But the gains in safety don’t just stop there.
It can function completely automatically (without driver input), applying and releasing the parking brakes as needed when the transmission is put in park or, in a vehicle with standard transmission, when the key is turned to the off position. It can apply the parking brake if the driver’s door is opened, if the driver’s seat belt is undone, or if the trunk or hood is opened. It can also be used as a hill holder to prevent the car from rolling back at a stop sign.
Furthermore, it can be incorporated with the anti-lock braking system (ABS) to provide low-speed traction control, or be used as an immobilizer, locking the wheels when the vehicle is parked, and the ignition is off.
And in the event of a hydraulic brake failure, it can bring the vehicle to a stop — much like an ABS stop — without the rear wheels locking up and causing a spin-out. The EPB could also be tied into the rear backup camera and apply the brake if the camera detects an obstacle.
In both designs, the EPB module will control the action of the bidirectional cable motor or caliper motors that apply the clamping force. The EPB module will monitor specific aspects of its own system, including the yaw rate of the vehicle, the position of the EPB switch, and the clamping force that is being applied to the brake cables or caliper pistons (typically using the amperage that the applying motors are consuming). It can also monitor the temperature of the clamping motors and control unit.
The EPB system also will perform self-diagnostics and will set and record trouble codes if it sees a problem. Codes can be set for any number of reasons, including overheated motors, shorts, opens, unintentional grounds, communication errors. This information also aids in diagnostics.
EPB provides a safer and more accurate parking brake system and while servicing them involves learning a few new tricks, it’s not too intimidating.
Proper up-to-date and valid service information is vital for proper and safe repairs of the EPB system. Vehicles equipped with EPB may experience unexpected parking brake application, which could result in personal injury and system damage. The EPB system must be in service or maintenance mode prior to servicing or removing rear brake components.
Cable puller EPB system tricks
Performing certain brake services will depend on the EPB system you are dealing with.
Rear brake pad service or even caliper replacement on GM’s Chevy and Cadillac models with the cable puller EPB system is performed similar to a non-powered parking brake system. But if any parking brake cable or EPB unit replacement is required, the EPB will need to be put into service mode.
This can be done manually using the service port on the EPB module and backing the motor off by hand, using the proper tool. Don’t be tempted to use a power tool, as it may cause damage to the EPB unit. A scan tool may also be used to get the EPB assembly into service mode and is the preferred method. But after the cables are replaced, the EPB needs to be tensioned and this can only be done using a scan tool following the specific reset calibration procedure.
Lexus has a similar manual release procedure available for their cable puller design, but again after the service work has been performed, a scan tool that will communicate bidirectional with the EPB module is going to be needed to finish the repair, and turn off the EPB light.
The BMW 750LI (other BMW models also use a cable puller design and the EPB unit is mounted under the rear cargo area) uses a cable puller EPB and the module is in the trunk. If anything gets spilled or the trunk has a water leak, the EPB module is in the low spot and can be damaged. This water intrusion can cause the EPB module to freeze, seize up or turn on the EPB light.
The BMW tool kit does supply the tool needed to manually release the EPB if it will move (they are usually seized solid) and the owner’s manual explains how to perform a manual release.
These BMW EPB motors also have a set of plastic gears that go bad and wear to look like an apple core. They are not available from BMW, but replacement gears are available online. The cost savings is substantial when the complete unit that the dealer will supply is more than $1,000. The EPB unit can be re-initialized manually after gear replacement by pressing the parking brake button three times with five-second intervals between pushes. The motor will try to release the brakes, then apply the brakes and finally release the brakes to complete the initialization. A BMW-compatible scanner also can be used.
Integrated EPB system caliper servicing tricks
Using a scan tool is typically going to be the manufacturer’s recommended method to retract the calipers to their service position to allow rear brake service or pad replacement. The scan tool is then used again to exit the service mode and automatically adjust the pads to the correct clearance after the rear brake service is performed.
But there are several makes and models that allow maintenance or service mode to be reached without a scan tool.
Ford integrated EPB system caliper servicing without a scan tool
EPB Service mode or EPB maintenance mode can be entered on the 2016 F-150 or the 2015 Ford Fusion hybrid using the following procedure without a scan tool.
To enter service mode:
1. Place the ignition switch to the ON position (engine off).
2. Depress and hold the accelerator pedal to the floor while holding the EPB switch in the release position. Continue to hold the accelerator pedal and EPB switch.
3. Turn the ignition switch to the OFF position and then return it to the ON position within five seconds while continuing to hold the accelerator pedal and the EPB switch.
4. At this point the EPB system will be in service mode. The yellow EPB indicator will be illuminated on the dash and the Maintenance Mode warning will show on the message center.
NOTE: When the system is in service mode, the parking brakes will not function until the mode has been deactivated.
1. Turn the ignition OFF and release both the accelerator pedal and the EPB switch.
2. Perform the needed rear brake service. The Ford caliper piston does not have to be rotated back into the caliper, but does need to be compressed using the proper tool. The use of a C-clamp or pliers may damage the caliper or motor, so they aren’t recommended.
Exiting service mode, after the repairs are made:
1.Place the ignition switch to the ON position (engine off).
2. Depress and hold the accelerator pedal to the floor while holding the EPB switch to the apply position. Continue to hold the accelerator pedal and EPB switch.
3. Turn the ignition switch to the OFF position and then return it to the ON position within five seconds while continuing to hold the accelerator pedal and the EPB switch.
4. The EPB system will apply the parking brake and release it into the proper position.
5. Release the accelerator pedal and the EPB switch.
Dodge/Jeep integrated EPB system caliper servicing without a scan tool
The EPB service mode can be entered following the menu driven instructions on the Uconnect driver’s information screen on some Dodge, Chrysler and Jeep models equipped with the integrated EPB system. You enter the brakes area from the settings screen and simply follow the on-screen instructions. After the repair is completed, the service mode must be exited again using the Uconnect screen (a scan tool can be used as well).
Honda integrated EPB system caliper servicing without a scan tool
Honda is using an EPB-integrated caliper on some of their newer models. A scan tool is the favored method of retracting the rear calipers for service, but they also have a factory recommended method if the appropriate scan tool isn’t available.
The factory service manual instructs you to:
1. Turn the key to the OFF position.
2. Remove the two bolts retaining the electric parking brake actuator from the back of the caliper assembly.
3. Using a T45 Torx driver, turn the spindle shaft on the caliper 360 degrees clockwise to release the parking brake. Make sure the parking brake is released, and if not, repeat the turn of the worm gear shaft 360 degrees.
4. Remove the caliper and using a compressor, press the piston straight back (turning is not required).
5. After the rear brake service is complete, reinstall the electric parking brake actuator, using a new sealing O-ring and screws, making sure the mating surface is clean.
6. Turn the key to the ON position.
7. Pull the EPB switch to the on position to apply the parking brakes and push on the brake pedal at the same time. This will exit brake pad maintenance mode.
8. Turn the ignition off.
Mazda integrated EPB system caliper servicing without a scan tool
Mazda provides a non-scan tool option for 2016/2017 CX-5s to retract the integrated caliper back for service, that is very similar to the process for Fords. This procedure can be followed to enter maintenance mode.
Entering service mode:
1. Switch the ignition ON, and don’t touch the brake pedal (the engine must be off throughout the procedure).
2. Release the EPB. Note Steps 3 and 4 must be done within five seconds.
3. While simultaneously pressing the accelerator pedal down fully, and pressing the EPB switch and holding both, switch the ignition OFF. You need to hold both the accelerator and EPB switch in this position during the next step.
4. Switch the ignition ON, while maintaining the depressed pedal and EPB switch.
5. If you have done everything correctly you should hear the caliper motors retracting. The yellow parking brake symbol with exclamation point will now be illuminated, indicating you are now in maintenance mode.
6. Switch the ignition off.
NOTE: Mazda does not want the piston rotated when servicing the caliper, just pushed back. Rotating the piston may damage the caliper internal parts.
Exiting service mode:
1. Switch ignition ON, engine off. Note Steps 2 and 3 must be done within 5 seconds.
2. While simultaneously pressing the accelerator pedal down fully, and pressing the EPB switch and holding, switch the ignition OFF. You need to hold both the accelerator and EPB switch in this position during the next step.
3. Switch the ignition ON, while maintaining the depressed pedal and EPB switch.
4. You should hear the caliper motors performing the automatic adjustment and the yellow warning light should go out, indicating maintenance mode has ended.
5. Switch the ignition OFF.
Other EPB tips and tricks
If working on some models of VW/Audi with an integrated EPB, not only will you need a scan tool to put the calipers into service mode and then re-initialize them, but you may also need to enter the actual brake pad material thickness.
The EPB system will use an algorithm to calculate the wear on the rear brake pads. This replaces the need for a pad wear sensor. Even if you have done the pad replacement properly, the brake wear warning light may stay on and trouble codes may be present until this brake pad thickness information is set into the EPB module. So, make a quick measurement of the pad thickness just in case you need this information.
Many EPB-equipped vehicles need software updates to fix issues that could cause either the EPB to stick, drag, not release, or illuminate the EPB light. GM’s Impala, some Cadillac models, Subarus and some Jeep Renegades have TSBs for reflashes and software updates. These updates correct different EPB issues from false applications to brake drag.
Honda has a recall to eliminate an issue that will cause the rear brakes to drag on some EPB-equipped Civics, and the fix is a software update.
Mazda’s also has a recall on its EPB system. A sealing issue on the rear integrated caliper design may allow water to enter, causing corrosion. This corrosion can cause the caliper to jam or fail to properly engage.
Some Jeep Renegade models have the EPB module located in the left rear cargo area and water could enter the module or the connector. This can cause the EPB not to release or result in service light concerns.
Bring this to a stop
Yes, a scan tool is going to be the manufacturer’s recommended method for repair or service, but many manufacturers provide a non-scan tool service mode, with the Fiat/Chrysler process by far the easiest.
A scan tool will be required for diagnostics, but most good scan tools can perform the needed tasks.
Reflashing the EPB software is a different story and may need dedicated manufacturer’s equipment and services.
Most techs will agree that working with an EPB-integrated caliper design is easier to service without a parking brake cable, and that’s something that most techs will embrace. ■
Jeff Taylor boasts a 32-year career in the automotive industry with Eccles Auto Service in Dundas, Ontario, as a fully licensed professional lead technician. While continuing to be “on the bench” every day, Taylor is also heavily involved in government focus groups, serves as an accomplished technical writer and has competed in international diagnostic competitions as well as providing his expertise as an automotive technical instructor for a major aftermarket parts retailer.
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