DTC U0122-00 (SRS Unit)

WARNING: This page is about a different car, the 2022 Honda Accord, 2021 Honda Accord, 2020 Honda Accord, 2019 Honda Accord, and 2018 Honda Accord. However, it is still accessible from the selected car via links, so may be relevant.

DTC U0122-00 : Lost Communication With the VSA Modulator-Control Unit (wheel speed sensor signal error)

NOTE:

Before doing this troubleshooting procedure, find out if the vehicle was in a collision. If so, verify that all the required components were replaced with new components of the correct part number and were properly installed .
Before doing this troubleshooting procedure, review SRS Precautions and Procedures , General Troubleshooting Information , and 12 Volt Battery Terminal Disconnection and Reconnection .
According to the detected DTC(s), check the power circuit and the ground circuit of the control unit which cannot communicate with the SRS unit.
Refer to the DTC shown on the display, then inspect the connectors and terminals based on the instructions.

DTC Description	DTC
U0122-00 Lost communication with the VSA modulator-control unit (Wheel speed sensor signal error)

DTC (SRS)

CAN gateway system DTC check

-1. Apply the parking brake.

-2. Turn the vehicle to the ON mode.

-3. Check for CAN gateway system DTCs with the HDS.

DTC Description	DTC

Are any DTCs indicated?

YES

Go to the troubleshooting for CAN gateway system DTC(s) .

Go to step 2.

F-CAN circuit communication check (Receiving control unit)
-1. Select the FUNCTION TEST in the CAN gateway with the HDS, then select the F-CAN Bus Connected Unit Check.

F-CAN Bus Connected Unit Check

Does the CAN gateway detect the SRS unit Bus channels B?

Bus B is Not Available

Go to step 3.

Bus B is Available

Go to step 4.

Open wire check (F-CAN B_H, F-CAN B_L lines)

-1. Turn the vehicle to the OFF (LOCK) mode.

-2. Disconnect the negative cable from the 12 volt battery, then wait at least 3 minutes.

-3. Disconnect the following connectors.

CAN gateway 16P connector

SRS unit connector A (43P)

-4. Check for continuity between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode
	CAN gateway 16P connector: disconnected
	SRS unit connector A (43P): disconnected
Test point 1	CAN gateway 16P connector (female terminals) No. 6 (on the dashboard wire harness):
Test point 2	SRS unit connector A (43P) No. 16

Test point 1	CAN gateway 16P connector (female terminals) No. 14 (on the dashboard wire harness):
Test point 2	SRS unit connector A (43P) No. 17

Courtesy of HONDA, U.S.A., INC.

Is there continuity?

YES

The F-CAN B_H and the F-CAN B_L wires are OK. Check for poor connections or loose terminals at the CAN gateway and the SRS unit. If the connection is OK, check for any authorized service information related to the DTCs or symptoms you are troubleshooting, or replace the SRS unit .

Replace an open in the wire between the CAN gateway and the SRS unit.

F-CAN circuit communication check (Transmitting control unit)

-1. Select the FUNCTION TEST in the CAN gateway with the HDS, then select the F-CAN Bus Connected Unit Check.

F-CAN Bus Connected Unit Check

According to the detected DTC on the following table, make sure that the transmitting control unit detects the CAN gateway Bus channel(s) normally.

DTC	Transmitting control unit	Detected CAN gateway Bus channel(s) at normal
U0122-00	VSA modulator-control unit	B

Is it detected normally?

Detected normal

Intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at the transmitting control unit and the CAN gateway.

U0122-00: VSA modulator-control unit is Not Available for Bus B

Go to step 5.

Open wire check (F-CAN B_H, F-CAN B_L lines)

-1. Turn the vehicle to the OFF (LOCK) mode.

-2. According to the detected DTC on the following table, disconnect the transmitting control unit connector(s).

DTC	Connector
-	CAN gateway 16P connector
U0122-00	VSA modulator-control unit 46P connector

-3. Check for continuity between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode
	CAN gateway 16P connector: disconnected
	Transmitting control unit connector(s) for indicated DTCs: disconnected

DTC	Circuit name	Test point 1 (Receiving control unit)		Test point 2 (Transmitting control unit)
DTC	Circuit name	Connector	Terminal	Connector	Terminal
U0122-00	F-CAN B_H	CAN gateway 16P connector (female terminals):	No. 6	VSA modulator-control unit 46P connector	No. 24
U0122-00	F-CAN B_L	CAN gateway 16P connector (female terminals):	No. 14	VSA modulator-control unit 46P connector	No. 25

Courtesy of HONDA, U.S.A., INC.

Is there continuity?

YES

The F-CAN B_H and the F-CAN B_L wires are OK. Check for poor connections or loose terminals at the SRS unit and the VSA modulator-control unit. Check for any authorized service information related to the DTCs or symptoms you are troubleshooting. If they are OK, replace the VSA modulator-control unit .

Repair an open in the wire between the transmitting control unit and the CAN gateway.