Classification:

Reference:

Date:

DA20-032B

ITB20-025B

July 13, 2021

DTC B2724-23 AND/OR C1B56-04 STORED, AND/OR
RAB ERROR MESSAGE OR WARNING
This bulletin has been amended. See AMENDMENT HISTORY on the last page.
Please discard previous versions of this bulletin.

APPLIED VEHICLES:

2020-2021 QX50 (J55)

APPLIED SYSTEM:

Rear Automatic Braking

IF YOU CONFIRM
One or both of the following DTCs are stored:


B2724-23 (SONAR CONTROL UNIT - SONAR ECU INTERNAL FAILURE [UNDER VOLTAGE])



C1B56-04 (SONAR CIRCUIT - SYSTEM INTERNAL MALFUNCTION)
NOTE: A RAB warning may appear in the vehicle information display.
Figure 1

ACTION
Reprogram the Sonar Control Unit, if applicable.

IMPORTANT: The purpose of ACTION (above) is to give you a quick idea of the work you will be performing.
You MUST closely follow the entire SERVICE PROCEDURE as it contains information that is essential to
successfully completing this repair.
Infiniti Bulletins are intended for use by qualified technicians, not 'do-it-yourselfers'. Qualified technicians are properly trained
individuals who have the equipment, tools, safety instruction, and know-how to do a job properly and safely. NOTE: If you believe that
a described condition may apply to a particular vehicle, DO NOT assume that it does. See your Infiniti retailer to determine if this
applies to your vehicle.

1/27

SERVICE PROCEDURE
Sonar Control Unit Reprogramming
IMPORTANT: Before starting, make sure:
 ASIST on the CONSULT PC has been synchronized (updated) to the current date.
 All CONSULT–III plus (C-III plus) software updates (if any) have been installed.
 The CONSULT PC is connected to the internet via a cable or Wi-Fi.
 Later in the procedure you will be required to enter your username and password.
 If you do not know your username and password, contact your service manager.
 A screen print for warranty documentation can be done from the CONSULT PC during this service
procedure while still connected to the vehicle.
 No diagnostic trouble codes (DTCs) are stored.
 Use C-III plus to perform Self Diagnosis for all systems.
 If there are any DTCs, other than B2724-23 and/or C1B56-04, diagnose, perform repairs, and
erase DTCs before continuing.
1.

Connect the Vehicle Interface (VI) to the vehicle.
 Make sure to use the correct VI for C-III plus.
Make sure the VI is securely connected. If the VI connection is loose during reprogramming, the
process will be interrupted and the control unit may be damaged.

2.

Connect the AC Adapter to the CONSULT PC.
Be sure to connect the AC Adapter. If the CONSULT PC battery voltage drops during reprogramming,
the process will be interrupted and the control unit may be damaged.

2/27

ITB20-025B

3.

Connect a battery maintainer or smart charger set to reflash mode or a similar setting.
To avoid damage to the control unit, ensure a battery maintainer or smart charger is connected. The
battery voltage must be between 12.0V and 15.5V during reprogramming.

4.

Turn OFF all external Bluetooth® devices (e.g., cell phones, printers, etc.) within range of the CONSULT
PC and the VI.
Make sure to turn OFF all external Bluetooth® devices. If Bluetooth® signal waves are within range of
the CONSULT PC and the VI during reprogramming, reprogramming may be interrupted and the
control unit may be damaged.

5.

Turn the ignition ON with the engine OFF.
To avoid damage to the control unit, the engine must not start or run during the reprogramming
procedure.

6.

Turn OFF all vehicle electrical loads such as exterior lights, interior lights, HVAC, blower, rear defogger,
audio, NAVI, seat heater, steering wheel heater, etc.

7.

Turn ON the hazard warning lamps.

8.

Turn ON the CONSULT PC.

9.

Start C-III plus.
 The serial number will display when the VI is recognized.

VI is
recognized

Figure 2

3/27

ITB20-025B

10.

Select Diagnosis (One System).

Figure 3
11.

Select SONAR.

Figure 4

4/27

ITB20-025B

12.

Select ECU Identification.

13.

Confirm the SOFTWARE #. See Figure 5.
 If the SOFTWARE # is A136, this bulletin does not apply. See the Electronic Service Manual (ESM)
for further diagnostic information.
 If the SOFTWARE # is not A136, proceed to step 14.

28538XXXXX

Bulletin does not
apply if this is A136

Figure 5
14.

Select Home.

28538XXXXX

Figure 6
5/27

ITB20-025B

15.

Select Re/programming, Configuration.

Figure 7
16.

Use the arrows (if needed) to view and read all precautions.

17.

Check the box confirming the precautions have been read.

18.

Select Next.

Figure 8
6/27

ITB20-025B

19.

Select Automatic Selection(VIN).

Example

Figure 9
20.

Confirm the VIN or Chassis # matches the vehicle’s VIN.

21.

Select Confirm.

XXXXXXXXXXXXXXXXX
XXXXXXXX
XXXXXXXX

Figure 10

7/27

ITB20-025B

22.

Select Confirm.

XXXXXXXXXXXXXXXXX

Figure 11
23.

Select SONAR.

Figure 12

8/27

ITB20-025B

24.

Select Reprogramming.

Figure 13
25.

When you get to the screen shown in Figure 14, confirm that a reprogram is available as follows.
A. Find the Sonar Control Unit Part Number and write it on the repair order.
NOTE: This is the current part number (P/N).

XXXXXXXXXXXXXXXXX

Current Sonar
Control Unit P/N

28538XXXXX

XXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXX

Figure 14
9/27

ITB20-025B

B. Compare the part number you wrote down to the part numbers in Table A.


If there is a match, continue with the reprogramming procedure.



If there is not a match in Table A, this bulletin does not apply. See the ESM for further
diagnostic information.

Table A
CURRENT SONAR CONTROL UNIT PART NUMBER: 285385NY0A, 5NY0B
5NY1A, 5NY1B

26.

Follow the on-screen instructions to navigate C-III plus and reprogram the Sonar Control Unit.

27.

Select Save.

XXXXXXXXXXXXXXXXX

28538XXXXX

XXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXX

Figure 15

28.

Read the precautions on the C-III plus screen, check the box for Confirmed Instructions, then
select Next. (Screens not shown.)

10/27

ITB20-025B

29.

Select Next.

28538-XXXXX
28538-XXXXX

XXXXXXXXXXXXXXXXX

Figure 16

HINT:


In some cases, more than one new part number for reprogramming is available.
 If more than one new part number is available, the screen in Figure 17 displays.
 Select and use the reprogramming option that does not have the message “Caution! Use ONLY
with ITBXX-XXX”.



If you get this screen and it is blank (no reprogramming listed), it means there is no reprogramming
available for this vehicle. Close C-III plus and refer back to the ESM for further diagnosis.

SONAR

Figure 17
11/27

ITB20-025B

30.

Make sure OK is highlighted green (battery voltage must be between 12.0 and 15.5 Volts).
To avoid damage to the control unit, ensure a battery maintainer or smart charger is connected. The
battery voltage must be between 12.0V and 15.5V during reprogramming.

31.

Select Next.

Monitor battery
voltage here

Figure 18

12/27

ITB20-025B

32.

Confirm all Judgment items are OK, then select Start.

Monitor battery
voltage here

Figure 19
33.

Select USA/CANADA Dealers.

34.

Select OK.

Figure 20
13/27

ITB20-025B

HINT:
 The screen in Figure 20 on page 13 may not display if the CONSULT PC has remained ON since the
last reprogramming.
 If the CONSULT PC is not connected to the internet, the screen in Figure 21 will display.

Figure 21
HINT: In the next steps, the reprogramming process will begin when Submit is selected.
35.

Enter your Username and Password.
 The CONSULT PC must be connected to the internet via cable or Wi-Fi.
 If you do not know your username and password, contact your service manager.

36.

Select Submit.

Figure 22

14/27

ITB20-025B

37.

Wait for both progress bars to complete.

Figure 23


When the screen in Figure 24 displays, the reprogramming is complete.



If the screen in Figure 24 does not display (indicating that reprogramming did not complete), refer to
Sonar Control Unit Recovery on the next page.

38.

Disconnect the battery maintainer or smart charger from the vehicle.