How Do Fj Cruiser Rear Parking Sensors Work?

The Toyota parking assist system is optionally available on the FJ Cruiser. This system uses parking sensors that are designed to give the driver an audible warning if the rear of the vehicle comes close to other objects -- such as another vehicle -- when parking or making maneuvers in reverse. The parking assist system may be a desirable option to those drivers who have ever tried to back up a large vehicle that has limited outward visibility at the rear.

How They Work

There are two parking sensors mounted into the rear bumper of your FJ Cruiser. The type of sensors used are ultrasonic, meaning that they emit amplified sound waves to detect obstacles or other vehicles behind you. The waves bounce off the offending object and back towards the sensor. This information is then sent to the sonar electronic control unit which is mounted under the passenger side of the dashboard. The sonar ECU processes the signals from the sensors and sounds a warning buzzer -- mounted on the dashboard to the right of the steering wheel -- if necessary.

Using Your Sensors

The Toyota parking assist system is operated by a switch in the center of the dashboard below the heater and air conditioning controls. Once switched on, electrical power is supplied to the sonar ECU. The warning buzzer should produce an audible tone for one second. This indicates to the driver that the system checks have been completed and everything should be working fine. If the buzzer stays on constantly, the ECU has detected a malfunction that requires immediate maintenance.

Sensor Range

The maximum detection range for the parking assist sensors is 59.1 inches for obstacles with a large surface area, such as a wall. This means you will not hear any audible alarm at distances greater than 59.1 inches. For obstacles with a smaller surface area, such as poles, the maximum detection range is even smaller at 43.3 inches. Upon first detection, the buzzer will emit a tone that goes on for 75 milliseconds and off for 225 milliseconds. This cycle continues while at a distance between 59.1 inches to 39.4 inches from the obstacle. When the sensors first detect that the obstacle is 39.4 inches away, the cycle changes. The buzzer will emit a tone cycle that goes on for 75 milliseconds and off for 75 milliseconds. Anything less than 19.7 inches and the tone will be constant, indicating that you should stop immediately.

Replace Parking Sensor

The two rear parking sensors may be the most vulnerable part of the parking assist system. The sensors are mounted in the rear bumper, where they are exposed to mud, dirt and salt that may shorten the life of the sensors. Replacement sensors are available from your Toyota dealer. To get to the sensors easier, remove the center plastic trim piece from the rear bumper cover -- which is held on with 11 mm bolts. Remove the retaining bolts from the bumper cover, then pull it straight off the rear of the vehicle to release the retaining clips. Once this is done, reach behind the bumper cover to unplug the sensor's wiring connector and push the sensor out of the its mounting hole from the back of the bumper cover. The new sensor can be installed in the reverse order.