DTC Advanced Diagnostics: U12B5-00
DTC U12B5-00: CAN Communication Failure With VSA (CAN Ch2)
NOTE
Initial Diagnosis:
The initial on-board diagnosis occurs right after the vehicle condition is turned to the ON mode, and the brake system indicator (red or amber) comes on, and continues until the indicator goes off.
Regular Diagnosis:
The regular on-board diagnosis begins right after the brake system indicator (red or amber) goes off, and it continues until the vehicle condition is turned to the OFF (LOCK) mode.
Review "How to Troubleshoot the Electric Brake Booster 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 6.0 - 18.9 V

With the Driving Pattern:
1.
Turn the vehicle to the ON mode.
Execution
Regular Diagnosis
Duration
About 1 second
DTC Type
1 drive cycle
Brake system indicator (amber) on
Fail Safe Action
Stop automatic brake hold function
Stop ACC function*1
Stop CMBS function*1
Possible Cause
Open, Short to ground, Short to power, or Short to another line between the electric brake booster and the VSA modulator-control unit (EBB CAN lines)*2
Open, Short to ground, Short to power, or Short to another line between the electric brake booster and the VSA modulator-control unit (F-CAN B lines)*3
VSA modulator-control unit internal failure
Electric brake booster internal failure
*1: With ACC
*2: Without CAN gateway
*3: With CAN gateway