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

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

   OK

   DTC C1242 is not output.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

GO 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 [10/2014 - ] 

Result: 

OK 

See step  2

1. Check for DTCs.

   HINT: 

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

   Result

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

Result: 

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 HV ECU [10/2015 - ]  

Result: 

A 

See step  3

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 (Brake Booster with Master Cylinder Assembly)

2. Disconnect the A51 skid control ECU (brake booster with master cylinder assembly) connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A51-35 (CA2H) - A51-34 (CA2L)	Cable disconnected from negative (-) auxiliary battery terminal	54 to 69 Ω

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE SKID CONTROL ECU (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY). Refer to  REMOVAL [10/2014 - ] 

Result: 

NG 

REPAIR OR REPLACE CAN BRANCH WIRE OR CONNECTOR (SKID CONTROL ECU (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY))