DTC U0129: Lost Communication with Brake System Control Module [06/2015 - 11/2018]: 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.

   Chassis > ABS/VSC/TRAC > Trouble Codes 

   OK

   DTC C1242 is not output.

   Result

   Result
   OK
   NG

Result: 

NG 

GO TO DIAGNOSIS PROCEDURE INDICATED BY OUTPUT DTC. Refer to  DIAGNOSTIC TROUBLE CODE CHART [06/2015 - ] 

Result: 

OK 

See step  2

Body Electrical > Gateway > Trouble Codes 

1. Reconfirm DTCs.

   HINT: 

   If DTC U1002 is output from Gateway of the network gateway ECU, this indicates a sub bus 2 malfunction. Troubleshoot for DTC U1002 and check for malfunctions in sub bus 2.

   Result

   Result	Proceed to
   U1002 is not output from network gateway ECU (Techstream display: Gateway)	A
   U1002 is output from network gateway ECU (Techstream display: Gateway)	B

Result: 

B 

GO TO DIAGNOSIS PROCEDURE INDICATED BY OUTPUT DTC. Refer to  DTC U1002: Lost Communication with Gateway Module (Network Gateway ECU) [06/2015 - 11/2018]  

Result: 

A 

See step  3

1. Disconnect the cable from the negative (-) auxiliary battery terminal.
2. Disconnect the 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
   A63-35 (CA2H) - A63-34 (CA2L)	Cable disconnected from negative (-) auxiliary battery terminal	54 to 69 Ω

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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

   Result

   Result
   OK
   NG

Result: 

OK 

REPLACE SKID CONTROL ECU (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY). Refer to  REMOVAL [06/2015 - 11/2018] 

Result: 

NG 

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