DTC U0129: Lost Communication with Brake System Control Module: Procedure

1. Disconnect the cable from the negative (-) battery terminal before measuring the resistances of the CAN main wire and CAN branch wire.
   WARNING:

   Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system.

   NOTE:

   When disconnecting the cable, some systems need to be initialized after the cable is reconnected, refer to INITIALIZATION .

NEXT: Go to next step 

1. Disconnect the A44 skid control ECU assembly connector.
   Fig 1: Identifying A44 Skid Control ECU Assembly Connector Terminal

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Switch Condition	Specified Condition
   A44-10 (CA2H) - A44-11 (CA2L)	Ignition switch off	54 to 69 Ω

   TEXT IN ILLUSTRATION
   
   

   *a	Rear view of wire harness connector (to Skid Control ECU Assembly)

NG → REPAIR OR REPLACE SKID CONTROL ECU ASSEMBLY BRANCH WIRE OR CONNECTOR (CA2H, CA2L) 

OK: Go to next step 

1. Connect the cable to the negative (-) battery terminal.
   NOTE:

   When disconnecting the cable, some systems need to be initialized after the cable is reconnected, refer to INITIALIZATION .

   Fig 2: Identifying A44, A45, A46 And A47 Skid Control ECU Assembly Connectors

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   TEXT IN ILLUSTRATION
   
   

   *a

   Rear view of wire harness connector (to Skid Control ECU Assembly)

   -

   -

2. Disconnect the A45, A46 and A47 skid control ECU assembly connectors.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A46-1 (GND) - Body ground	Always	Below 1 Ω
   A44-3 (GND2) - Body ground	Always	Below 1 Ω
   A44-1 (GND3) - Body ground	Always	Below 1 Ω
   A47-3 (GND4) - Body ground	Always	Below 1 Ω
   A47-1 (GND5) - Body ground	Always	Below 1 Ω
   A45-3 (GND6) - Body ground	Always	Below 1 Ω

4. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   A44-2 (IG1) - Body ground	Ignition switch ON	11 to 14 V
   A47-5 (IG2) - Body ground	Ignition switch ON	11 to 14 V
   A44-4 (+BI1) - Body ground	Always	11 to 14 V
   A45-5 (+BI2) - Body ground	Always	11 to 14 V
   A44-5 (+BI3) - Body ground	Always	11 to 14 V
   A45-6 (+BI4) - Body ground	Always	11 to 14 V

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK → See step   4