DTC U0129: Lost Communication with Brake System Control Module: 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 C1241 is not output.

NG → See step   5 

OK: Go to next step 

1. Reconfirm DTCs.

   HINT: 

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

   Result

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

B → See step   4 

A: Go to next step 

1. Disconnect the cable from the negative (-) auxiliary battery terminal.
   Fig 1: A24 Brake Booster With Master Cylinder Assembly (Skid Control ECU) Connector

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Disconnect the A24 brake booster with master cylinder assembly (skid control ECU) connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A24-35(CA2H) - A24-34(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))

NG → REPAIR OR REPLACE CAN BRANCH LINE OR CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY) 

OK → See step   6