DTC Advanced Diagnostics: U0129-00
DTC U0129-00: CAN Communication Failure with AHB/ESB/EBB
NOTE
Initial Diagnosis:
The initial on-board diagnosis occurs right after the vehicle condition is turned to the ON mode, and the ABS/VSA indicator comes on, and continues until the indicator goes off.
Regular Diagnosis:
The regular on-board diagnosis begins right after the ABS/VSA indicator goes off, and it continues until the vehicle condition is turned to the OFF (LOCK) mode.
Review "How to troubleshoot the VSA system" before doing the DTC troubleshooting procedure.
Test-drive the vehicle according to local traffic conditions and regulations. Do not test-drive on a lift unless specified.
The possible causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.

Confirmation Procedure
Basic Condition:
12 volt battery voltage 9.6 - 16.5 V

With the Driving Pattern:
1.
Start the engine.
Execution
Regular Diagnosis
Duration
About 1 second
DTC Type
1 drive cycle
Brake system indicator (amber) on (Dependant upon the conditions)
VSA indicator on (Dependant upon the conditions)
Fail Safe Action
Degrade ABS performance (Dependant upon the conditions)
Stop engine drag torque control function (Dependant upon the conditions)
Stop TCS function (Dependant upon the conditions)
Stop VSA function (Dependant upon the conditions)
Stop agile handling assist function (Dependant upon the conditions)
Stop brake assist function (Dependant upon the conditions)
Stop hill start assist function (Dependant upon the conditions)
Stop automatic brake hold function (Dependant upon the conditions)
Stop ACC function (Dependant upon the conditions)*1
Stop CMBS function (Dependant upon the conditions)*1
Possible Cause
Open or Poor connection between the VSA modulator-control unit and the electric brake booster (F-CAN lines)
Open or Poor connection between the VSA modulator-control unit and the electric brake booster (EBB CAN lines)*2
Open or Poor connection between the VSA modulator-control unit and the electric brake booster (F-CAN B lines)*3
Electric brake booster internal failure
VSA modulator-control unit internal failure
*1: With ACC
*2: Without CAN gateway
*3: With CAN gateway