Kia Rio: Body Electrical System / Rear Parking Assist System

Kia Rio 2017-2024 YB Service Manual / Body Electrical System / Rear Parking Assist System


Ultrasonic sensor
Voltage rating
DC 12V
Detecting range
11.8 - 47.2 in (30 - 120 cm)
Operation voltage
DC 9 - 16 V
Operation current
MAX 350 mA
Operating temperature
-22 - 176°F (-30 - 80°C)
Operating frequency
48 ± 5 kHz
Number of sensors
4 EA

Components and components location
Component Location

1. Body Control Module (BCM)
2. Ultrasonic sensor


Rear parking assist control unit function is built in BCM (Body Control Module).

Description and operation
System Overview

RPAS (Rear Parking Assist System) is an electronic driving aid that warns the driver to be cautious while parking or driving at low speed. The sensor uses ultrasonic waves to detect objects within proximity of the vehicle.

RPAS consists of four RPAS sensors which are detecting the obstacles and transmit the result separated into three warning levels, the first, second and third to BCM by Lin communication. BCM decides the alarm level by the transmitted communication message from the slave sensors, and then operates the buzzer or transmits the data for display.

System Operation Specification.


INIT mode


System initializing time is 500ms after IGN1+ R Gear.


RPAS recognizes LID and sets the sensor ID up during initialization.


RPAS activates each sensor and then executes the diagnosis after finishing initialization of BCM


If the diagnosis is completed and sensor does not send an error message, “RPAS Startling Buzzer” is normally worked.


If failure is received from any sensors, R-PAS Starting Buzzer” does not work but the failure alarm is operated for a moment.

If you have display option, warning sign is also shown on it.


Buzzer for sensor failure is operated once, but the sensor failure state is shown in display until the failure is repaired.




Lin communication starts and keeps the routine after IGN1 ON+R gear


BCM sends a message once to each sensor for operating request to check the initial status of the system and four sensors response all at once. At this time, if there is no problem, the alarm starts after 500 ms of R gear shifting at 300 ms intervals.


After initialization, normal mode starts 100ms later after finishing alarm output.


Alarm for obstacles is divided into 3 levels.

The first and second are intermittent sound, and the third alarms continuously


The efficient vehicle speed of RPAS operation is below 10Km/h.


Refer to ‘Digital PAS Project LIN communication’ for the more detailed communication specification.

Sensing Area


Measurement condition – PVC pole (diameter 75mm, length 1m), normal temperature


Distance range detected objects (Measured directly in front of sensor)

61cm(24.0in) - 120cm(47.2in) : ± 15cm(5.9in)

31cm(12.2in) - 60cm(23.6in): ± 15cm(5.9in)

Less than 30cm(11.8in) : ± 10cm(3.9in)

Horizontal Sensing Area

Vertical Sensing Area

Distance Measurement

Direct Measurement

Transmission and Reception are executed with one sensor

(RL, RCL, RCR, RR each sensor execution)

Indirect Measurement

(RCL → RL, RCL → RCR, RCR → RCL, RCR → RR Execution in order)

With two or three sensors, one of them sends the transmission and the others get the reception.

Direct and Indirect Measurement at once

With two or three sensors, the one sensor performs both transmission and reception, and the others perform only reception.

RPAS alarm system

When the RPAS sensor detects the object, warning is operated by audible alarm device as like buzzer. RPAS sensor sends data to BCM via LIN communication and BCM implements audible warning for each RPAS SENSOR by priority. And it performs a role of gateway only when it sends visible alarm device such as Cluster.

Sensor buzzer/display information processing method of BCM In case of RL/RR sensor information, the BCM handles each sensor information directly about Display and buzzer output function. Buzzer output of CL/CR sensor, BCM handles center combination information by priority both sensor.

System Operation Spec

When the system has the power (after IGN ON and R gear), MICOM checks every sensor channel. In case it finds any error, it gives off the buzzer for 300ms after 500ms.If an error is found even in a sensor, it gives off the buzzer corresponding to the faulty sensor, instead of initial starting alarm. The operation to enter the normal mode is as follows.

With the R gear put in the car, the system is operated as follows.

With the R gear released, the system is operated as follows.

※ The acceptable error range on waveform is ±10%.

Alarm Output Specification classified by distance between sensors

Condition logic according to priority of alarm level is as below. (the identical sensor)

*α value definition


low priority sensor off : α = 0ms


low priority sensor is 1st warning level : α < 340ms


low priority sensor is 2nd warning level : α < 170ms

*β value definition


low priority sensor is 1st warning level : β = 1700ms


low priority sensor is 2nd warning level : β = 1700ms


low priority sensor is 3rd warning level : β = 700ms

Alarm control by sensing distance is as follows.


First warning area (31.9 in (81 cm) - 47.2 in (120 cm) )


Second warning area (16.1 in (41 cm) - 31.5 in (80 cm) )


Third warning area (less than 15.7 in (40 cm))

Visible Alarm Indicator Specification

When the gear shifts to R, the cluster controls the indicator as the following picture.

When the system detects an object, it immediately turns on the indicator. If an object disappears while the RPAS detecting operation, the indicator remains on for 2 sec. before being turned off.

(But when it turns third step alarm to No alarm status, it lights third step alarm for two second and turns out.)

It shows only the detecting position of obstacles.

In third level alarm, indicator flickers at intervals of a second.

In normal alarm mode, integrated display of RCR/RCL

Communication Standard

This section defines the communication between RPAS and BCM.

RPAS send a detecting result of object and sensor diagnosis result to BCM according to this document, and BCM takes a role to issue an alarm.

Indicator shows the transmitted position and alarm data, in the alarm mode, it finds the nearest DATA and alarms the nearest DATA first.

(Ex. In case, RL isthe first-step alarm and RR is the third step, RR alarm has priority.)

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