DTC U0129: Lost Communication with Brake System Control Module [10/2015 - ]: Procedure

1. Check for DTCs.

   HINT: 

   If the power management control ECU outputs DTC U0100, U0129 and U0293 check the branch circuit of sub bus 15.

   Result

   Result	Proceed to
   The power management control ECU outputs only DTC U0129.	A
   The power management control ECU outputs DTC U0100, U0129 and U0293.	B

Result:  2

B 

GO TO DIAGNOSIS PROCEDURE INDICATED BY OUTPUT DTC. Refer to  DTC U0100: Lost Communication with ECM / PCM "A"; DTC U0129: Lost Communication with Brake System Control Module; DTC U0293: Lost Communication with Hybrid Vehicle Control System [10/2015 - ]  

Result:  1

A 

See step  2

1. Disconnect the cable from the negative (-) auxiliary battery terminal.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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

2. Disconnect the skid control ECU assembly connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A16-9 (CANH) - A16-8 (CANL)	Cable disconnected from negative (-) auxiliary battery terminal	54 to 69 Ω

   Result

   Proceed to
   OK
   NG

Result:  2

NG 

REPAIR OR REPLACE CAN BRANCH WIRE CONNECTED TO SKID CONTROL ECU ASSEMBLY (CANH, CANL) 

Result:  1

OK 

See step  3

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

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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

   NOTE:

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

   Refer to INITIALIZATION [10/2015 - ]

2. Disconnect the skid control ECU assembly connector.
3. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Switch Condition	Specified Condition
   A14-43 (+BI1) - Body ground	Power switch off	11 to 14 V
   A14-29 (+BI3) - Body ground	Power switch off	11 to 14 V
   A16-38 (+BI2) - Body ground	Power switch off	11 to 14 V
   A16-22 (+BI4) - Body ground	Power switch off	11 to 14 V
   A14-46 (IG1) - Body ground	Power switch on (IG)	11 to 14 V
   A16-46 (IG2) - Body ground	Power switch on (IG)	11 to 14 V

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A14-1 (GND) - Body ground	Always	Below 1 Ω
   A16-1 (GND4) - Body ground	Always	Below 1 Ω

   Result

   Proceed to
   OK
   NG

Result:  2

OK 

REPLACE SKID CONTROL ECU ASSEMBLY. Refer to  REMOVAL [09/2014 - ] 

Result:  1

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR