DTC U0129: Lost Communication with Brake System Control Module [11/2015 - ]: Procedure

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON (IG).
3. Turn the Techstream on.
4. Enter the following menus: Chassis / ABS/VSC/TRAC / Trouble Codes.

   OK

   DTC C1241 is not output.

Result: 

NG 

REFER TO DIAGNOSIS PROCEDURE INDICATED BY OUTPUT DTC 

Refer to DTC C1241/41: Low Battery Positive Voltage; DTC C1242/42: Open in IG1 / IG2 Power Source Circuit [11/2015 - ] )

Result: 

OK 

See step  2

1. Reconfirm DTCs.

   HINT: 

   If the hybrid vehicle control ECU outputs DTC U0100 and DTC U0129, check the branch circuit of sub bus 15.

   Result

   Result	Proceed to
   The hybrid vehicle control ECU outputs only DTC U0129. (Techstream display: Hybrid Control)	A
   The hybrid vehicle control ECU outputs DTC U0100 and U0129. (Techstream display: Hybrid Control)	B

Result: 

B 

REFER 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 HV ECU [11/2015 - 06/2017] Refer to DTC U0100: Lost Communication with ECM / PCM "A"; DTC U0129: Lost Communication with Brake System Control Module; DTC U0293: Lost Communication with HV ECU [06/2017 - ] )

Result: 

A 

See step  3

1. Disconnect the cable from the negative (-) auxiliary battery terminal.
2. Disconnect the A41 brake booster with master cylinder assembly (skid control ECU) connector.

   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
   A41-35 (CA2H) - A41-34 (CA2L)	Cable disconnected from negative (-) auxiliary battery terminal	54 to 69 Ω

   TEXT IN ILLUSTRATION
   
   

   *a	Front view of wire harness connector (to Brake Booster with Master Cylinder Assembly (Skid Control ECU))

Result: 

OK 

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY 

Refer to REMOVAL [11/2015 - ] )

Result: 

NG 

REPAIR OR REPLACE CAN BRANCH LINES OR CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY)