Technical
There’s no stopping the electric parking brake EPB system can make servicing vehicles easier! 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 reasons behind EPB and the two common designs
By Jeff Taylor
T
he 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.
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 drumin-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
22 | ASP February 2018
