DTC Troubleshooting: U0122-00
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 for 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)
  

1.
CAN gateway system DTC check:

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
U0029-00 CAN Gateway F-CAN ch A Bus Off
  
U0047-00 CAN Gateway F-CAN ch B Bus Off
  
U3000-49 CAN Gateway Internal Failure
  

Is DTC U0029-00, U0047-00, and/or U3000-49 indicated?

     
YES
     
     
     
     
NO
     
     
     
Go to step 2.
2.
F-CAN circuit communication check (Receiving control unit):

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.

  

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

     
Bus B is Not Available
     
     
     
Go to step 3.
     
Bus B is Available
     
     
     
Go to step 4.
3.
Open wire check (F-CAN B_H, F-CAN B_L lines):

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.

?3.
Disconnect the following connectors.
CAN gateway 12P connector
SRS unit connector A (39P)

?4.
Check for continuity 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 12P connector (female terminals) No. 12 (on the dashboard wire harness):
Test point 2
SRS unit connector A (39P) No. 34

Test point 1
CAN gateway 12P connector (female terminals) No. 5 (on the dashboard wire harness):
Test point 2
SRS unit connector A (39P) No. 35


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.?
     
NO
     
     
     
Replace an open in the wire between the CAN gateway and the SRS unit.?
4.
F-CAN circuit communication check (Transmitting control 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.

  

?2.
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 getaway Bus channel(s) at normal
U0122-00
VSA modulator-control unit
A, 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 A
     
     
     
Go to step 5.
     
U0122-00: VSA modulator-control unit is Not Available for Bus B
     
     
     
Go to step 6.
5.
Open wire check (F-CAN A_H, F-CAN A_L lines):

Open wire check (F-CAN A_H, F-CAN A_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 12P 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 12P connector: disconnected
 
Transmitting control unit connector(s) for indicated DTCs: disconnected

DTC
Circuit name
Receiving control unit
Transmitting control unit
Connector
Terminal
Connector
Terminal
U0122-00
F-CAN A_H
CAN gateway 12P connector (female terminals):
No. 3
VSA modulator-control unit 46P connector
No. 40
F-CAN A_L
No. 9
No. 28


Is there continuity?

     
YES
     
     
     
The F-CAN_H and the F-CAN_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.
     
NO
     
     
     
Repair an open in the wire between the transmitting control unit and the CAN gateway.?
6.
Open wire check (F-CAN B_H, F-CAN B_L lines):

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 12P 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 12P connector: disconnected
 
Transmitting control unit connector(s) for indicated DTCs: disconnected

DTC
Circuit name
Receiving control unit
Transmitting control unit
Connector
Terminal
Connector
Terminal
U0122-00
F-CAN B_H
CAN gateway 12P connector (female terminals):
No. 12
VSA modulator-control unit 46P connector
No. 34
F-CAN B_L
No. 5
No. 35


Is there continuity?

     
YES
     
     
     
According to the detected DTC on the following table, substitute or replace the correspond control unit.?
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.
DTC
Operation for transmitting control unit
U0122-00
Replace the VSA modulator-control unit.
     
NO
     
     
     
Repair an open in the wire between the transmitting control unit and the CAN gateway.?