DTC U0122: Lost Communication with Vehicle Dynamics Control Module; 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 main wire and the branch wire.
   WARNING:

   Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to prevent airbag and seat belt pretensioner activation.

   NOTE:

   • w/ Navigation System (for HDD):

     After the power switch is turned off, the display and navigation module display (HDD navigation system) records various types of memory and settings. As a result, after turning the power switch off, be sure to wait for the time specified in the table before disconnecting the cable from the negative (-) battery terminal.

     Waiting Time before Disconnecting Cable from Negative (-) Battery Terminal

     Condition	Waiting Time
     Vehicle enrolled in safety connect system	6 minute
     Vehicle not enrolled in safety connect system	1 minute

   • 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 A19 and A21 skid control ECU connectors.
   Fig 1: Identifying A19 And A21 Skid Control ECU Connector Terminals

   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
   A21-30 (CA1H) - A21-29 (CA1L)	Power switch OFF	54 to 69 Ω
   A19-7 (CA2H) - A19-6 (CA2L)	Power switch OFF	54 to 69 Ω

NG → REPAIR OR REPLACE SKID CONTROL ECU BRANCH WIRE OR CONNECTOR (CA1H, CA1L, 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 .

2. Disconnect the A19 and A21 skid control ECU connectors.
   Fig 2: Identifying A19 And A21 Skid Control ECU Connector Terminals

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A19-1 (GND) - Body ground	Always	Below 1 Ω
   A21-1 (GND4) - Body ground	Always	Below 1 Ω

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

   Standard Voltage

   Tester Connection	Switch Condition	Specified Condition
   A19-43 (+BI1) - Body ground	Always	11 to 14 V
   A21-38 (+BI2) - Body ground	Always	11 to 14 V
   A19-29 (+BI3) - Body ground	Always	11 to 14 V
   A21-22 (+BI4) - Body ground	Always	11 to 14 V
   A19-46 (IG1) - Body ground	Power switch ON (IG)	11 to 14 V
   A21-46 (IG2) - Body ground	Power switch ON (IG)	11 to 14 V

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK → See step   4