Mercedes-Benz SL450 Parking Brake Activation Switch Replacement Cost

Electronically activated parking brakes are becoming more common, especially from manufacturers of luxury vehicles. These systems do not use the regular pressed, pulled, or lifted manual actuators, they are engaged by a button that typically has a 'P' with a circle, or some other designation for the parking brake. When the button is pressed, the parking brake is set. In most cases, the parking brake is released by either pressing the button again, or by moving the button in a different direction.

When the parking brake button is pressed, it sends a signal through a wire to the parking brake control module. This control module will determine the meaning of the incoming signal, and then output a signal to the parking brake control motor to set the parking brakes. Once the parking brakes are set, the brake rotors will be locked in position so the tires will be unable to move. Next, when the driver would like to move the vehicle, the parking brake release function is used, and that sends an opposing signal to the parking brake control module. The parking brake control module, again, interprets the signal, and signals the parking brake control motor to release the parking brakes. The rotors are now free to move, and the wheels and tires can rotate freely.

Only three symptoms are possible of the parking brake switch. The parking brake switch may fail to engage the parking brake. This would be because the parking brake control module never gets the signal to set the brakes. Next, the parking brake switch may fail to release the brake, if the activation switch doubles as the deactivation switch. Finally, erratic operation of the parking brake switch when not pressed may occur, so warning messages would appear on the instrument cluster if the switch requests the parking brake while driving.

The parking brake is a necessary inspection item, but it is also a safety feature for the vehicle while it is parked. If the parking brakes cannot be activated, the vehicle should go in for repairs promptly. However, if the vehicle is experiencing random requests for the parking brake or the parking brake cannot be released with the parking brake activation/deactivation switch, service is required right away.

Like other switches mounted near the driver, these switches are subject to dust and moisture from the windows, spilled drinks, and constant use. It would be no surprise to see a failed parking brake activation switch, especially if it were mounted on the center console, however, they are not particularly common. In most cases, this switch will last the lifetime of the vehicle, and physical damage and constant use are the main two causes of failure.

Parking brake failure would cause the technician to diagnose the small parking brake system, and likely by connecting a diagnostic scan tool. This method would allow him or her to monitor the result of pressing the parking brake activation switch, and, if it doubles as a deactivation switch, that function can be monitored as well. If it is found that the switch sends no signal or sends an improper signal, the switch will be back probed at the connector to ensure that the control module reading is the same as the reading at the parking brake switch. If so, the parking brake activation switch will be replaced.

Replacement will only involve removing the switch with a non-marring pry tool, or by removing the surrounding trim panel to extract its' mounting fasteners. Afterwards, the electrical connector is removed, and replaced on the new switch. The connector and surrounding area may need to be cleaned as well.

When dealing with electronic systems, we recommend thorough diagnostics before replacing parts. In effort to correct an electronic failure, it would be very easy to spend hundreds of dollars replacing components before realizing the issue is more advanced. In the case of electronic failures, diagnostics is a must.

Though these systems are becoming more common, most vehicles use mechanical levers to actuate the parking brake, and these systems have their own sets of issue and causes. Also, electronic parking brakes may not actuate if the service brake wear indicators have alerted the body control module of low brake pad thickness. This would seem as if the switch were faulty, except a message would appear as feedback to the parking brake switch.

The parking brake switch can be diagnosed and replaced by almost anyone. It is a simple two or three way switch, and it can be tested without a diagnostic scan tool. In most cases, a diagnostic scan tool is used for efficiency and speed rather than necessity, so understanding the circuit will allow the DIY mechanic to accomplish this repair at home.