DTC U0122-00 (SRS Unit)

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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 .
Check for the power circuit and the ground circuit of the VSA modulator-control unit which cannot communicate with the SRS unit.

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. Turn the vehicle to the ON mode.

-2. 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 SRS unit detect the CAN gateway Bus channels C?

Bus C is Not Available

Go to step 3.

Bus C is Available

Go to step 4.

Open wire check (F-CAN C_H, F-CAN C_L lines)

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

-2. Disconnect the negative cable from the 12 volt battery.

-3. Disconnect the following connectors.

CAN gateway 16P connector

SRS unit connector A (39P)

-4. Measure the resistance between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode
	CAN gateway 12P connector: disconnected
	SRS unit connector A (39P): disconnected
Test point 1	CAN gateway 16P connector (female terminals) No. 5 (on the dashboard wire harness):
Test point 2	SRS unit connector A (39P) No. 34

Test point 1	CAN gateway 16P connector (female terminals) No. 13 (on the dashboard wire harness):
Test point 2	SRS unit connector A (39P) No. 35

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

Is there 1.0 Ω or less?

YES

The F-CAN C_H and the F-CAN C_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
-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

Which result is indicated?

VSA modulator-control unit is Detected

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.

VSA modulator-control unit (Bus B) is Not Available

Go to step 5.

VSA modulator-control unit (Bus C) is Not Available

Go to step 6.

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

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

-2. Disconnect the following connectors.

CAN gateway 16P connector

VSA modulator-control unit 46P connector

-3. Measure the resistance between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode
	CAN gateway 16P connector: disconnected
	VSA modulator-control unit 46P connector
Test point 1	CAN gateway 16P connector (female terminals) No. 6:
Test point 2	VSA modulator-control unit 46P connector No. 40

Test point 1	CAN gateway 16P connector (female terminals) No. 14:
Test point 2	VSA modulator-control unit 46P connector No. 28

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

Is there 1.0 Ω or less?

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 or replace the VSA modulator-control unit .

Repair an open in the wire between the VSA modulator-control unit and the CAN gateway.

Open wire check (F-CAN C_H, F-CAN C_L lines)

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

-2. Disconnect the following connectors.

CAN gateway 16P connector

VSA modulator-control unit 46P connector

-3. Measure the resistance between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode
	CAN gateway 16P connector: disconnected
	VSA modulator-control unit 46P connector
Test point 1	CAN gateway 16P connector (female terminals) No. 5:
Test point 2	VSA modulator-control unit 46P connector No. 46

Test point 1	CAN gateway 16P connector (female terminals) No. 13:
Test point 2	VSA modulator-control unit 46P connector No. 34

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

Is there 1.0 Ω or less?

YES

The F-CAN C_H and the F-CAN C_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 or replace the VSA modulator-control unit .

Repair an open in the wire between the VSA modulator-control unit and the CAN gateway.